diff --git a/src/animation/AnimationObjectGroup.js b/src/animation/AnimationObjectGroup.js
index 4f49d964fa131..d43a114f076b7 100644
--- a/src/animation/AnimationObjectGroup.js
+++ b/src/animation/AnimationObjectGroup.js
@@ -34,6 +34,8 @@ class AnimationObjectGroup {
 
 	constructor() {
 
+		this.isAnimationObjectGroup = true;
+
 		this.uuid = MathUtils.generateUUID();
 
 		// cached objects followed by the active ones
@@ -382,6 +384,4 @@ class AnimationObjectGroup {
 
 }
 
-AnimationObjectGroup.prototype.isAnimationObjectGroup = true;
-
 export { AnimationObjectGroup };
diff --git a/src/cameras/ArrayCamera.js b/src/cameras/ArrayCamera.js
index 0d5ad131d4131..4da2d1d4a8d99 100644
--- a/src/cameras/ArrayCamera.js
+++ b/src/cameras/ArrayCamera.js
@@ -6,13 +6,12 @@ class ArrayCamera extends PerspectiveCamera {
 
 		super();
 
+		this.isArrayCamera = true;
+
 		this.cameras = array;
 
 	}
 
 }
 
-ArrayCamera.prototype.isArrayCamera = true;
-
-
 export { ArrayCamera };
diff --git a/src/cameras/Camera.js b/src/cameras/Camera.js
index 3f745c93d2e17..7748346736145 100644
--- a/src/cameras/Camera.js
+++ b/src/cameras/Camera.js
@@ -7,6 +7,8 @@ class Camera extends Object3D {
 
 		super();
 
+		this.isCamera = true;
+
 		this.type = 'Camera';
 
 		this.matrixWorldInverse = new Matrix4();
@@ -63,6 +65,4 @@ class Camera extends Object3D {
 
 }
 
-Camera.prototype.isCamera = true;
-
 export { Camera };
diff --git a/src/cameras/OrthographicCamera.js b/src/cameras/OrthographicCamera.js
index 523fd2330ee2f..f9520343fbc81 100755
--- a/src/cameras/OrthographicCamera.js
+++ b/src/cameras/OrthographicCamera.js
@@ -6,6 +6,8 @@ class OrthographicCamera extends Camera {
 
 		super();
 
+		this.isOrthographicCamera = true;
+
 		this.type = 'OrthographicCamera';
 
 		this.zoom = 1;
@@ -131,6 +133,4 @@ class OrthographicCamera extends Camera {
 
 }
 
-OrthographicCamera.prototype.isOrthographicCamera = true;
-
 export { OrthographicCamera };
diff --git a/src/cameras/PerspectiveCamera.js b/src/cameras/PerspectiveCamera.js
index 9c16b8c38bfe7..4a6becc3a099d 100644
--- a/src/cameras/PerspectiveCamera.js
+++ b/src/cameras/PerspectiveCamera.js
@@ -7,6 +7,8 @@ class PerspectiveCamera extends Camera {
 
 		super();
 
+		this.isPerspectiveCamera = true;
+
 		this.type = 'PerspectiveCamera';
 
 		this.fov = fov;
@@ -228,6 +230,4 @@ class PerspectiveCamera extends Camera {
 
 }
 
-PerspectiveCamera.prototype.isPerspectiveCamera = true;
-
 export { PerspectiveCamera };
diff --git a/src/core/BufferAttribute.js b/src/core/BufferAttribute.js
index 92fb5f0611f67..e9a184b95da9a 100644
--- a/src/core/BufferAttribute.js
+++ b/src/core/BufferAttribute.js
@@ -17,6 +17,8 @@ class BufferAttribute {
 
 		}
 
+		this.isBufferAttribute = true;
+
 		this.name = '';
 
 		this.array = array;
@@ -399,8 +401,6 @@ class BufferAttribute {
 
 }
 
-BufferAttribute.prototype.isBufferAttribute = true;
-
 //
 
 class Int8BufferAttribute extends BufferAttribute {
@@ -479,11 +479,12 @@ class Float16BufferAttribute extends BufferAttribute {
 
 		super( new Uint16Array( array ), itemSize, normalized );
 
+		this.isFloat16BufferAttribute = true;
+
 	}
 
 }
 
-Float16BufferAttribute.prototype.isFloat16BufferAttribute = true;
 
 class Float32BufferAttribute extends BufferAttribute {
 
diff --git a/src/core/BufferGeometry.js b/src/core/BufferGeometry.js
index 91b4578f6edcc..68bf0168ed879 100644
--- a/src/core/BufferGeometry.js
+++ b/src/core/BufferGeometry.js
@@ -25,6 +25,8 @@ class BufferGeometry extends EventDispatcher {
 
 		super();
 
+		this.isBufferGeometry = true;
+
 		Object.defineProperty( this, 'id', { value: _id ++ } );
 
 		this.uuid = MathUtils.generateUUID();
@@ -1125,6 +1127,4 @@ class BufferGeometry extends EventDispatcher {
 
 }
 
-BufferGeometry.prototype.isBufferGeometry = true;
-
 export { BufferGeometry };
diff --git a/src/core/GLBufferAttribute.js b/src/core/GLBufferAttribute.js
index d301dbda15697..5e627d82bcbd4 100644
--- a/src/core/GLBufferAttribute.js
+++ b/src/core/GLBufferAttribute.js
@@ -2,6 +2,8 @@ class GLBufferAttribute {
 
 	constructor( buffer, type, itemSize, elementSize, count ) {
 
+		this.isGLBufferAttribute = true;
+
 		this.buffer = buffer;
 		this.type = type;
 		this.itemSize = itemSize;
@@ -53,6 +55,4 @@ class GLBufferAttribute {
 
 }
 
-GLBufferAttribute.prototype.isGLBufferAttribute = true;
-
 export { GLBufferAttribute };
diff --git a/src/core/InstancedBufferAttribute.js b/src/core/InstancedBufferAttribute.js
index 01eee65b267e1..8123f4a23857d 100644
--- a/src/core/InstancedBufferAttribute.js
+++ b/src/core/InstancedBufferAttribute.js
@@ -16,6 +16,8 @@ class InstancedBufferAttribute extends BufferAttribute {
 
 		super( array, itemSize, normalized );
 
+		this.isInstancedBufferAttribute = true;
+
 		this.meshPerAttribute = meshPerAttribute;
 
 	}
@@ -44,6 +46,4 @@ class InstancedBufferAttribute extends BufferAttribute {
 
 }
 
-InstancedBufferAttribute.prototype.isInstancedBufferAttribute = true;
-
 export { InstancedBufferAttribute };
diff --git a/src/core/InstancedBufferGeometry.js b/src/core/InstancedBufferGeometry.js
index 34943d1f91447..f061ccaadcba7 100644
--- a/src/core/InstancedBufferGeometry.js
+++ b/src/core/InstancedBufferGeometry.js
@@ -6,6 +6,8 @@ class InstancedBufferGeometry extends BufferGeometry {
 
 		super();
 
+		this.isInstancedBufferGeometry = true;
+
 		this.type = 'InstancedBufferGeometry';
 		this.instanceCount = Infinity;
 
@@ -41,6 +43,4 @@ class InstancedBufferGeometry extends BufferGeometry {
 
 }
 
-InstancedBufferGeometry.prototype.isInstancedBufferGeometry = true;
-
 export { InstancedBufferGeometry };
diff --git a/src/core/InstancedInterleavedBuffer.js b/src/core/InstancedInterleavedBuffer.js
index 9d404af70bc0f..7f667161ee773 100644
--- a/src/core/InstancedInterleavedBuffer.js
+++ b/src/core/InstancedInterleavedBuffer.js
@@ -6,6 +6,8 @@ class InstancedInterleavedBuffer extends InterleavedBuffer {
 
 		super( array, stride );
 
+		this.isInstancedInterleavedBuffer = true;
+
 		this.meshPerAttribute = meshPerAttribute;
 
 	}
@@ -43,6 +45,4 @@ class InstancedInterleavedBuffer extends InterleavedBuffer {
 
 }
 
-InstancedInterleavedBuffer.prototype.isInstancedInterleavedBuffer = true;
-
 export { InstancedInterleavedBuffer };
diff --git a/src/core/InterleavedBuffer.js b/src/core/InterleavedBuffer.js
index d252f3cd5b300..6fae629793c56 100644
--- a/src/core/InterleavedBuffer.js
+++ b/src/core/InterleavedBuffer.js
@@ -5,6 +5,8 @@ class InterleavedBuffer {
 
 	constructor( array, stride ) {
 
+		this.isInterleavedBuffer = true;
+
 		this.array = array;
 		this.stride = stride;
 		this.count = array !== undefined ? array.length / stride : 0;
@@ -140,6 +142,4 @@ class InterleavedBuffer {
 
 }
 
-InterleavedBuffer.prototype.isInterleavedBuffer = true;
-
 export { InterleavedBuffer };
diff --git a/src/core/InterleavedBufferAttribute.js b/src/core/InterleavedBufferAttribute.js
index 1fe89b7f6e60f..6d13609721273 100644
--- a/src/core/InterleavedBufferAttribute.js
+++ b/src/core/InterleavedBufferAttribute.js
@@ -7,6 +7,8 @@ class InterleavedBufferAttribute {
 
 	constructor( interleavedBuffer, itemSize, offset, normalized = false ) {
 
+		this.isInterleavedBufferAttribute = true;
+
 		this.name = '';
 
 		this.data = interleavedBuffer;
@@ -276,7 +278,5 @@ class InterleavedBufferAttribute {
 
 }
 
-InterleavedBufferAttribute.prototype.isInterleavedBufferAttribute = true;
-
 
 export { InterleavedBufferAttribute };
diff --git a/src/core/Object3D.js b/src/core/Object3D.js
index c315bbda6ab33..ea06b5453d6e6 100644
--- a/src/core/Object3D.js
+++ b/src/core/Object3D.js
@@ -31,6 +31,8 @@ class Object3D extends EventDispatcher {
 
 		super();
 
+		this.isObject3D = true;
+
 		Object.defineProperty( this, 'id', { value: _object3DId ++ } );
 
 		this.uuid = MathUtils.generateUUID();
@@ -922,6 +924,4 @@ class Object3D extends EventDispatcher {
 Object3D.DefaultUp = new Vector3( 0, 1, 0 );
 Object3D.DefaultMatrixAutoUpdate = true;
 
-Object3D.prototype.isObject3D = true;
-
 export { Object3D };
diff --git a/src/extras/curves/ArcCurve.js b/src/extras/curves/ArcCurve.js
index b1101c0d5fc6b..edb84f4630cf3 100644
--- a/src/extras/curves/ArcCurve.js
+++ b/src/extras/curves/ArcCurve.js
@@ -6,12 +6,12 @@ class ArcCurve extends EllipseCurve {
 
 		super( aX, aY, aRadius, aRadius, aStartAngle, aEndAngle, aClockwise );
 
+		this.isArcCurve = true;
+
 		this.type = 'ArcCurve';
 
 	}
 
 }
 
-ArcCurve.prototype.isArcCurve = true;
-
 export { ArcCurve };
diff --git a/src/extras/curves/CatmullRomCurve3.js b/src/extras/curves/CatmullRomCurve3.js
index 8ed78fa68717c..a0bfd4af887b2 100644
--- a/src/extras/curves/CatmullRomCurve3.js
+++ b/src/extras/curves/CatmullRomCurve3.js
@@ -87,6 +87,8 @@ class CatmullRomCurve3 extends Curve {
 
 		super();
 
+		this.isCatmullRomCurve3 = true;
+
 		this.type = 'CatmullRomCurve3';
 
 		this.points = points;
@@ -248,6 +250,4 @@ class CatmullRomCurve3 extends Curve {
 
 }
 
-CatmullRomCurve3.prototype.isCatmullRomCurve3 = true;
-
 export { CatmullRomCurve3 };
diff --git a/src/extras/curves/CubicBezierCurve.js b/src/extras/curves/CubicBezierCurve.js
index e9bd2eec2ff38..a2d45f53f77bc 100644
--- a/src/extras/curves/CubicBezierCurve.js
+++ b/src/extras/curves/CubicBezierCurve.js
@@ -8,6 +8,8 @@ class CubicBezierCurve extends Curve {
 
 		super();
 
+		this.isCubicBezierCurve = true;
+
 		this.type = 'CubicBezierCurve';
 
 		this.v0 = v0;
@@ -73,6 +75,4 @@ class CubicBezierCurve extends Curve {
 
 }
 
-CubicBezierCurve.prototype.isCubicBezierCurve = true;
-
 export { CubicBezierCurve };
diff --git a/src/extras/curves/CubicBezierCurve3.js b/src/extras/curves/CubicBezierCurve3.js
index 1c4af2c2d85a8..c5afdf26c902b 100644
--- a/src/extras/curves/CubicBezierCurve3.js
+++ b/src/extras/curves/CubicBezierCurve3.js
@@ -8,6 +8,8 @@ class CubicBezierCurve3 extends Curve {
 
 		super();
 
+		this.isCubicBezierCurve3 = true;
+
 		this.type = 'CubicBezierCurve3';
 
 		this.v0 = v0;
@@ -74,6 +76,4 @@ class CubicBezierCurve3 extends Curve {
 
 }
 
-CubicBezierCurve3.prototype.isCubicBezierCurve3 = true;
-
 export { CubicBezierCurve3 };
diff --git a/src/extras/curves/EllipseCurve.js b/src/extras/curves/EllipseCurve.js
index afce9dc381322..5833648193c6f 100644
--- a/src/extras/curves/EllipseCurve.js
+++ b/src/extras/curves/EllipseCurve.js
@@ -7,6 +7,8 @@ class EllipseCurve extends Curve {
 
 		super();
 
+		this.isEllipseCurve = true;
+
 		this.type = 'EllipseCurve';
 
 		this.aX = aX;
@@ -151,6 +153,4 @@ class EllipseCurve extends Curve {
 
 }
 
-EllipseCurve.prototype.isEllipseCurve = true;
-
 export { EllipseCurve };
diff --git a/src/extras/curves/LineCurve.js b/src/extras/curves/LineCurve.js
index cde9b2ef13b8e..4b14d5edb6aad 100644
--- a/src/extras/curves/LineCurve.js
+++ b/src/extras/curves/LineCurve.js
@@ -7,6 +7,8 @@ class LineCurve extends Curve {
 
 		super();
 
+		this.isLineCurve = true;
+
 		this.type = 'LineCurve';
 
 		this.v1 = v1;
@@ -85,6 +87,4 @@ class LineCurve extends Curve {
 
 }
 
-LineCurve.prototype.isLineCurve = true;
-
 export { LineCurve };
diff --git a/src/extras/curves/LineCurve3.js b/src/extras/curves/LineCurve3.js
index 1a101dfa96939..c315c3869f302 100644
--- a/src/extras/curves/LineCurve3.js
+++ b/src/extras/curves/LineCurve3.js
@@ -7,9 +7,10 @@ class LineCurve3 extends Curve {
 
 		super();
 
-		this.type = 'LineCurve3';
 		this.isLineCurve3 = true;
 
+		this.type = 'LineCurve3';
+
 		this.v1 = v1;
 		this.v2 = v2;
 
diff --git a/src/extras/curves/QuadraticBezierCurve.js b/src/extras/curves/QuadraticBezierCurve.js
index d311bd8230eda..6ed67d988ec7b 100644
--- a/src/extras/curves/QuadraticBezierCurve.js
+++ b/src/extras/curves/QuadraticBezierCurve.js
@@ -8,6 +8,8 @@ class QuadraticBezierCurve extends Curve {
 
 		super();
 
+		this.isQuadraticBezierCurve = true;
+
 		this.type = 'QuadraticBezierCurve';
 
 		this.v0 = v0;
@@ -69,6 +71,4 @@ class QuadraticBezierCurve extends Curve {
 
 }
 
-QuadraticBezierCurve.prototype.isQuadraticBezierCurve = true;
-
 export { QuadraticBezierCurve };
diff --git a/src/extras/curves/QuadraticBezierCurve3.js b/src/extras/curves/QuadraticBezierCurve3.js
index 32b936c019af4..bdc882cc21eed 100644
--- a/src/extras/curves/QuadraticBezierCurve3.js
+++ b/src/extras/curves/QuadraticBezierCurve3.js
@@ -8,6 +8,8 @@ class QuadraticBezierCurve3 extends Curve {
 
 		super();
 
+		this.isQuadraticBezierCurve3 = true;
+
 		this.type = 'QuadraticBezierCurve3';
 
 		this.v0 = v0;
@@ -70,6 +72,4 @@ class QuadraticBezierCurve3 extends Curve {
 
 }
 
-QuadraticBezierCurve3.prototype.isQuadraticBezierCurve3 = true;
-
 export { QuadraticBezierCurve3 };
diff --git a/src/extras/curves/SplineCurve.js b/src/extras/curves/SplineCurve.js
index 182d459d7b6d9..073b9e46bdf2c 100644
--- a/src/extras/curves/SplineCurve.js
+++ b/src/extras/curves/SplineCurve.js
@@ -8,6 +8,8 @@ class SplineCurve extends Curve {
 
 		super();
 
+		this.isSplineCurve = true;
+
 		this.type = 'SplineCurve';
 
 		this.points = points;
@@ -92,6 +94,4 @@ class SplineCurve extends Curve {
 
 }
 
-SplineCurve.prototype.isSplineCurve = true;
-
 export { SplineCurve };
diff --git a/src/helpers/SkeletonHelper.js b/src/helpers/SkeletonHelper.js
index 75a5b31b07936..188395d7b7e1f 100644
--- a/src/helpers/SkeletonHelper.js
+++ b/src/helpers/SkeletonHelper.js
@@ -47,9 +47,10 @@ class SkeletonHelper extends LineSegments {
 
 		super( geometry, material );
 
-		this.type = 'SkeletonHelper';
 		this.isSkeletonHelper = true;
 
+		this.type = 'SkeletonHelper';
+
 		this.root = object;
 		this.bones = bones;
 
diff --git a/src/lights/AmbientLight.js b/src/lights/AmbientLight.js
index 6dc043676612f..1c73748619f62 100644
--- a/src/lights/AmbientLight.js
+++ b/src/lights/AmbientLight.js
@@ -6,12 +6,12 @@ class AmbientLight extends Light {
 
 		super( color, intensity );
 
+		this.isAmbientLight = true;
+
 		this.type = 'AmbientLight';
 
 	}
 
 }
 
-AmbientLight.prototype.isAmbientLight = true;
-
 export { AmbientLight };
diff --git a/src/lights/AmbientLightProbe.js b/src/lights/AmbientLightProbe.js
index 7b19b4fb54219..d5aac6aa71857 100644
--- a/src/lights/AmbientLightProbe.js
+++ b/src/lights/AmbientLightProbe.js
@@ -7,6 +7,8 @@ class AmbientLightProbe extends LightProbe {
 
 		super( undefined, intensity );
 
+		this.isAmbientLightProbe = true;
+
 		const color1 = new Color().set( color );
 
 		// without extra factor of PI in the shader, would be 2 / Math.sqrt( Math.PI );
@@ -16,6 +18,4 @@ class AmbientLightProbe extends LightProbe {
 
 }
 
-AmbientLightProbe.prototype.isAmbientLightProbe = true;
-
 export { AmbientLightProbe };
diff --git a/src/lights/DirectionalLight.js b/src/lights/DirectionalLight.js
index 7c477f71c38ae..7031c8bbacfcf 100644
--- a/src/lights/DirectionalLight.js
+++ b/src/lights/DirectionalLight.js
@@ -8,6 +8,8 @@ class DirectionalLight extends Light {
 
 		super( color, intensity );
 
+		this.isDirectionalLight = true;
+
 		this.type = 'DirectionalLight';
 
 		this.position.copy( Object3D.DefaultUp );
@@ -38,6 +40,4 @@ class DirectionalLight extends Light {
 
 }
 
-DirectionalLight.prototype.isDirectionalLight = true;
-
 export { DirectionalLight };
diff --git a/src/lights/DirectionalLightShadow.js b/src/lights/DirectionalLightShadow.js
index 1b63dd897de11..10ade5b470367 100644
--- a/src/lights/DirectionalLightShadow.js
+++ b/src/lights/DirectionalLightShadow.js
@@ -7,10 +7,10 @@ class DirectionalLightShadow extends LightShadow {
 
 		super( new OrthographicCamera( - 5, 5, 5, - 5, 0.5, 500 ) );
 
+		this.isDirectionalLightShadow = true;
+
 	}
 
 }
 
-DirectionalLightShadow.prototype.isDirectionalLightShadow = true;
-
 export { DirectionalLightShadow };
diff --git a/src/lights/HemisphereLight.js b/src/lights/HemisphereLight.js
index 9d1ca94d0df3e..1ca6fb7af2a25 100644
--- a/src/lights/HemisphereLight.js
+++ b/src/lights/HemisphereLight.js
@@ -8,6 +8,8 @@ class HemisphereLight extends Light {
 
 		super( skyColor, intensity );
 
+		this.isHemisphereLight = true;
+
 		this.type = 'HemisphereLight';
 
 		this.position.copy( Object3D.DefaultUp );
@@ -29,6 +31,4 @@ class HemisphereLight extends Light {
 
 }
 
-HemisphereLight.prototype.isHemisphereLight = true;
-
 export { HemisphereLight };
diff --git a/src/lights/HemisphereLightProbe.js b/src/lights/HemisphereLightProbe.js
index 6173409cddfce..4846332686ccc 100644
--- a/src/lights/HemisphereLightProbe.js
+++ b/src/lights/HemisphereLightProbe.js
@@ -8,6 +8,8 @@ class HemisphereLightProbe extends LightProbe {
 
 		super( undefined, intensity );
 
+		this.isHemisphereLightProbe = true;
+
 		const color1 = new Color().set( skyColor );
 		const color2 = new Color().set( groundColor );
 
@@ -25,6 +27,4 @@ class HemisphereLightProbe extends LightProbe {
 
 }
 
-HemisphereLightProbe.prototype.isHemisphereLightProbe = true;
-
 export { HemisphereLightProbe };
diff --git a/src/lights/Light.js b/src/lights/Light.js
index f16d75d42d716..0b2bbdf88f648 100644
--- a/src/lights/Light.js
+++ b/src/lights/Light.js
@@ -7,6 +7,8 @@ class Light extends Object3D {
 
 		super();
 
+		this.isLight = true;
+
 		this.type = 'Light';
 
 		this.color = new Color( color );
@@ -53,6 +55,4 @@ class Light extends Object3D {
 
 }
 
-Light.prototype.isLight = true;
-
 export { Light };
diff --git a/src/lights/LightProbe.js b/src/lights/LightProbe.js
index fbef062ef9b60..5f0714367ffbf 100644
--- a/src/lights/LightProbe.js
+++ b/src/lights/LightProbe.js
@@ -7,6 +7,8 @@ class LightProbe extends Light {
 
 		super( undefined, intensity );
 
+		this.isLightProbe = true;
+
 		this.sh = sh;
 
 	}
@@ -42,6 +44,4 @@ class LightProbe extends Light {
 
 }
 
-LightProbe.prototype.isLightProbe = true;
-
 export { LightProbe };
diff --git a/src/lights/PointLight.js b/src/lights/PointLight.js
index 02817cf204920..b533f1dd8470e 100644
--- a/src/lights/PointLight.js
+++ b/src/lights/PointLight.js
@@ -7,6 +7,8 @@ class PointLight extends Light {
 
 		super( color, intensity );
 
+		this.isPointLight = true;
+
 		this.type = 'PointLight';
 
 		this.distance = distance;
@@ -52,6 +54,4 @@ class PointLight extends Light {
 
 }
 
-PointLight.prototype.isPointLight = true;
-
 export { PointLight };
diff --git a/src/lights/PointLightShadow.js b/src/lights/PointLightShadow.js
index 995a0bca050b3..86847d10c8c9d 100644
--- a/src/lights/PointLightShadow.js
+++ b/src/lights/PointLightShadow.js
@@ -15,6 +15,8 @@ class PointLightShadow extends LightShadow {
 
 		super( new PerspectiveCamera( 90, 1, 0.5, 500 ) );
 
+		this.isPointLightShadow = true;
+
 		this._frameExtents = new Vector2( 4, 2 );
 
 		this._viewportCount = 6;
@@ -91,6 +93,4 @@ class PointLightShadow extends LightShadow {
 
 }
 
-PointLightShadow.prototype.isPointLightShadow = true;
-
 export { PointLightShadow };
diff --git a/src/lights/RectAreaLight.js b/src/lights/RectAreaLight.js
index 711ca5bbb06cc..084685b347ea0 100644
--- a/src/lights/RectAreaLight.js
+++ b/src/lights/RectAreaLight.js
@@ -6,6 +6,8 @@ class RectAreaLight extends Light {
 
 		super( color, intensity );
 
+		this.isRectAreaLight = true;
+
 		this.type = 'RectAreaLight';
 
 		this.width = width;
@@ -51,6 +53,4 @@ class RectAreaLight extends Light {
 
 }
 
-RectAreaLight.prototype.isRectAreaLight = true;
-
 export { RectAreaLight };
diff --git a/src/lights/SpotLight.js b/src/lights/SpotLight.js
index 7c35259335800..9d6685c8401d2 100644
--- a/src/lights/SpotLight.js
+++ b/src/lights/SpotLight.js
@@ -8,6 +8,8 @@ class SpotLight extends Light {
 
 		super( color, intensity );
 
+		this.isSpotLight = true;
+
 		this.type = 'SpotLight';
 
 		this.position.copy( Object3D.DefaultUp );
@@ -64,6 +66,4 @@ class SpotLight extends Light {
 
 }
 
-SpotLight.prototype.isSpotLight = true;
-
 export { SpotLight };
diff --git a/src/lights/SpotLightShadow.js b/src/lights/SpotLightShadow.js
index 8dd8d3e9e0385..7fa37b32f6f29 100644
--- a/src/lights/SpotLightShadow.js
+++ b/src/lights/SpotLightShadow.js
@@ -8,6 +8,8 @@ class SpotLightShadow extends LightShadow {
 
 		super( new PerspectiveCamera( 50, 1, 0.5, 500 ) );
 
+		this.isSpotLightShadow = true;
+
 		this.focus = 1;
 
 	}
@@ -45,6 +47,4 @@ class SpotLightShadow extends LightShadow {
 
 }
 
-SpotLightShadow.prototype.isSpotLightShadow = true;
-
 export { SpotLightShadow };
diff --git a/src/loaders/ImageBitmapLoader.js b/src/loaders/ImageBitmapLoader.js
index 2a9d15a374284..6ca5585432a68 100644
--- a/src/loaders/ImageBitmapLoader.js
+++ b/src/loaders/ImageBitmapLoader.js
@@ -7,6 +7,8 @@ class ImageBitmapLoader extends Loader {
 
 		super( manager );
 
+		this.isImageBitmapLoader = true;
+
 		if ( typeof createImageBitmap === 'undefined' ) {
 
 			console.warn( 'THREE.ImageBitmapLoader: createImageBitmap() not supported.' );
@@ -94,6 +96,4 @@ class ImageBitmapLoader extends Loader {
 
 }
 
-ImageBitmapLoader.prototype.isImageBitmapLoader = true;
-
 export { ImageBitmapLoader };
diff --git a/src/materials/LineBasicMaterial.js b/src/materials/LineBasicMaterial.js
index cd433105f755b..fe876f47979e1 100644
--- a/src/materials/LineBasicMaterial.js
+++ b/src/materials/LineBasicMaterial.js
@@ -7,6 +7,8 @@ class LineBasicMaterial extends Material {
 
 		super();
 
+		this.isLineBasicMaterial = true;
+
 		this.type = 'LineBasicMaterial';
 
 		this.color = new Color( 0xffffff );
@@ -40,6 +42,4 @@ class LineBasicMaterial extends Material {
 
 }
 
-LineBasicMaterial.prototype.isLineBasicMaterial = true;
-
 export { LineBasicMaterial };
diff --git a/src/materials/LineDashedMaterial.js b/src/materials/LineDashedMaterial.js
index 5b7326af596f0..53f534d0a2ee3 100644
--- a/src/materials/LineDashedMaterial.js
+++ b/src/materials/LineDashedMaterial.js
@@ -6,6 +6,8 @@ class LineDashedMaterial extends LineBasicMaterial {
 
 		super();
 
+		this.isLineDashedMaterial = true;
+
 		this.type = 'LineDashedMaterial';
 
 		this.scale = 1;
@@ -30,6 +32,4 @@ class LineDashedMaterial extends LineBasicMaterial {
 
 }
 
-LineDashedMaterial.prototype.isLineDashedMaterial = true;
-
 export { LineDashedMaterial };
diff --git a/src/materials/Material.js b/src/materials/Material.js
index 39bfd6e4c06ce..f5baabb7fae1c 100644
--- a/src/materials/Material.js
+++ b/src/materials/Material.js
@@ -10,6 +10,8 @@ class Material extends EventDispatcher {
 
 		super();
 
+		this.isMaterial = true;
+
 		Object.defineProperty( this, 'id', { value: materialId ++ } );
 
 		this.uuid = MathUtils.generateUUID();
@@ -496,8 +498,6 @@ class Material extends EventDispatcher {
 
 }
 
-Material.prototype.isMaterial = true;
-
 Material.fromType = function ( /*type*/ ) {
 
 	// TODO: Behavior added in Materials.js
diff --git a/src/materials/MeshBasicMaterial.js b/src/materials/MeshBasicMaterial.js
index 804f75e217028..b9f7c2b5706fd 100644
--- a/src/materials/MeshBasicMaterial.js
+++ b/src/materials/MeshBasicMaterial.js
@@ -8,6 +8,8 @@ class MeshBasicMaterial extends Material {
 
 		super();
 
+		this.isMeshBasicMaterial = true;
+
 		this.type = 'MeshBasicMaterial';
 
 		this.color = new Color( 0xffffff ); // emissive
@@ -76,6 +78,4 @@ class MeshBasicMaterial extends Material {
 
 }
 
-MeshBasicMaterial.prototype.isMeshBasicMaterial = true;
-
 export { MeshBasicMaterial };
diff --git a/src/materials/MeshDepthMaterial.js b/src/materials/MeshDepthMaterial.js
index 597954036fd33..b56155d00ce58 100644
--- a/src/materials/MeshDepthMaterial.js
+++ b/src/materials/MeshDepthMaterial.js
@@ -7,6 +7,8 @@ class MeshDepthMaterial extends Material {
 
 		super();
 
+		this.isMeshDepthMaterial = true;
+
 		this.type = 'MeshDepthMaterial';
 
 		this.depthPacking = BasicDepthPacking;
@@ -49,6 +51,4 @@ class MeshDepthMaterial extends Material {
 
 }
 
-MeshDepthMaterial.prototype.isMeshDepthMaterial = true;
-
 export { MeshDepthMaterial };
diff --git a/src/materials/MeshDistanceMaterial.js b/src/materials/MeshDistanceMaterial.js
index 3e0d69d766952..3b54005235ed3 100644
--- a/src/materials/MeshDistanceMaterial.js
+++ b/src/materials/MeshDistanceMaterial.js
@@ -7,6 +7,8 @@ class MeshDistanceMaterial extends Material {
 
 		super();
 
+		this.isMeshDistanceMaterial = true;
+
 		this.type = 'MeshDistanceMaterial';
 
 		this.referencePosition = new Vector3();
@@ -47,6 +49,4 @@ class MeshDistanceMaterial extends Material {
 
 }
 
-MeshDistanceMaterial.prototype.isMeshDistanceMaterial = true;
-
 export { MeshDistanceMaterial };
diff --git a/src/materials/MeshLambertMaterial.js b/src/materials/MeshLambertMaterial.js
index 02bb914166380..cb17537a4564b 100644
--- a/src/materials/MeshLambertMaterial.js
+++ b/src/materials/MeshLambertMaterial.js
@@ -8,6 +8,8 @@ class MeshLambertMaterial extends Material {
 
 		super();
 
+		this.isMeshLambertMaterial = true;
+
 		this.type = 'MeshLambertMaterial';
 
 		this.color = new Color( 0xffffff ); // diffuse
@@ -84,6 +86,4 @@ class MeshLambertMaterial extends Material {
 
 }
 
-MeshLambertMaterial.prototype.isMeshLambertMaterial = true;
-
 export { MeshLambertMaterial };
diff --git a/src/materials/MeshMatcapMaterial.js b/src/materials/MeshMatcapMaterial.js
index a421c7798e600..84030dcae04ab 100644
--- a/src/materials/MeshMatcapMaterial.js
+++ b/src/materials/MeshMatcapMaterial.js
@@ -9,6 +9,8 @@ class MeshMatcapMaterial extends Material {
 
 		super();
 
+		this.isMeshMatcapMaterial = true;
+
 		this.defines = { 'MATCAP': '' };
 
 		this.type = 'MeshMatcapMaterial';
@@ -76,6 +78,4 @@ class MeshMatcapMaterial extends Material {
 
 }
 
-MeshMatcapMaterial.prototype.isMeshMatcapMaterial = true;
-
 export { MeshMatcapMaterial };
diff --git a/src/materials/MeshNormalMaterial.js b/src/materials/MeshNormalMaterial.js
index 4674fb390d6ad..b891031b01302 100644
--- a/src/materials/MeshNormalMaterial.js
+++ b/src/materials/MeshNormalMaterial.js
@@ -8,6 +8,8 @@ class MeshNormalMaterial extends Material {
 
 		super();
 
+		this.isMeshNormalMaterial = true;
+
 		this.type = 'MeshNormalMaterial';
 
 		this.bumpMap = null;
@@ -56,6 +58,4 @@ class MeshNormalMaterial extends Material {
 
 }
 
-MeshNormalMaterial.prototype.isMeshNormalMaterial = true;
-
 export { MeshNormalMaterial };
diff --git a/src/materials/MeshPhongMaterial.js b/src/materials/MeshPhongMaterial.js
index 541927ec108b2..6dfe9e46c27c0 100644
--- a/src/materials/MeshPhongMaterial.js
+++ b/src/materials/MeshPhongMaterial.js
@@ -9,6 +9,8 @@ class MeshPhongMaterial extends Material {
 
 		super();
 
+		this.isMeshPhongMaterial = true;
+
 		this.type = 'MeshPhongMaterial';
 
 		this.color = new Color( 0xffffff ); // diffuse
@@ -115,6 +117,4 @@ class MeshPhongMaterial extends Material {
 
 }
 
-MeshPhongMaterial.prototype.isMeshPhongMaterial = true;
-
 export { MeshPhongMaterial };
diff --git a/src/materials/MeshPhysicalMaterial.js b/src/materials/MeshPhysicalMaterial.js
index b6e84da2cebdd..c26a30c5d75b8 100644
--- a/src/materials/MeshPhysicalMaterial.js
+++ b/src/materials/MeshPhysicalMaterial.js
@@ -9,6 +9,8 @@ class MeshPhysicalMaterial extends MeshStandardMaterial {
 
 		super();
 
+		this.isMeshPhysicalMaterial = true;
+
 		this.defines = {
 
 			'STANDARD': '',
@@ -163,6 +165,4 @@ class MeshPhysicalMaterial extends MeshStandardMaterial {
 
 }
 
-MeshPhysicalMaterial.prototype.isMeshPhysicalMaterial = true;
-
 export { MeshPhysicalMaterial };
diff --git a/src/materials/MeshStandardMaterial.js b/src/materials/MeshStandardMaterial.js
index e64e8f4727ab2..1821cf2ffa446 100644
--- a/src/materials/MeshStandardMaterial.js
+++ b/src/materials/MeshStandardMaterial.js
@@ -9,6 +9,8 @@ class MeshStandardMaterial extends Material {
 
 		super();
 
+		this.isMeshStandardMaterial = true;
+
 		this.defines = { 'STANDARD': '' };
 
 		this.type = 'MeshStandardMaterial';
@@ -119,6 +121,4 @@ class MeshStandardMaterial extends Material {
 
 }
 
-MeshStandardMaterial.prototype.isMeshStandardMaterial = true;
-
 export { MeshStandardMaterial };
diff --git a/src/materials/MeshToonMaterial.js b/src/materials/MeshToonMaterial.js
index 45a61338c8df0..2f9b2f9e273b5 100644
--- a/src/materials/MeshToonMaterial.js
+++ b/src/materials/MeshToonMaterial.js
@@ -9,6 +9,8 @@ class MeshToonMaterial extends Material {
 
 		super();
 
+		this.isMeshToonMaterial = true;
+
 		this.defines = { 'TOON': '' };
 
 		this.type = 'MeshToonMaterial';
@@ -97,6 +99,4 @@ class MeshToonMaterial extends Material {
 
 }
 
-MeshToonMaterial.prototype.isMeshToonMaterial = true;
-
 export { MeshToonMaterial };
diff --git a/src/materials/PointsMaterial.js b/src/materials/PointsMaterial.js
index a671ee89dbebb..8ca5500d6ee12 100644
--- a/src/materials/PointsMaterial.js
+++ b/src/materials/PointsMaterial.js
@@ -7,6 +7,8 @@ class PointsMaterial extends Material {
 
 		super();
 
+		this.isPointsMaterial = true;
+
 		this.type = 'PointsMaterial';
 
 		this.color = new Color( 0xffffff );
@@ -45,6 +47,4 @@ class PointsMaterial extends Material {
 
 }
 
-PointsMaterial.prototype.isPointsMaterial = true;
-
 export { PointsMaterial };
diff --git a/src/materials/RawShaderMaterial.js b/src/materials/RawShaderMaterial.js
index 0ab5bdf323204..e2ab4377aeb98 100644
--- a/src/materials/RawShaderMaterial.js
+++ b/src/materials/RawShaderMaterial.js
@@ -6,12 +6,12 @@ class RawShaderMaterial extends ShaderMaterial {
 
 		super( parameters );
 
+		this.isRawShaderMaterial = true;
+
 		this.type = 'RawShaderMaterial';
 
 	}
 
 }
 
-RawShaderMaterial.prototype.isRawShaderMaterial = true;
-
 export { RawShaderMaterial };
diff --git a/src/materials/ShaderMaterial.js b/src/materials/ShaderMaterial.js
index ccc89b7b17dd0..378b4575f5055 100644
--- a/src/materials/ShaderMaterial.js
+++ b/src/materials/ShaderMaterial.js
@@ -10,6 +10,8 @@ class ShaderMaterial extends Material {
 
 		super();
 
+		this.isShaderMaterial = true;
+
 		this.type = 'ShaderMaterial';
 
 		this.defines = {};
@@ -181,6 +183,4 @@ class ShaderMaterial extends Material {
 
 }
 
-ShaderMaterial.prototype.isShaderMaterial = true;
-
 export { ShaderMaterial };
diff --git a/src/materials/ShadowMaterial.js b/src/materials/ShadowMaterial.js
index da81b1b1d3cdf..deea305d9e633 100644
--- a/src/materials/ShadowMaterial.js
+++ b/src/materials/ShadowMaterial.js
@@ -7,6 +7,8 @@ class ShadowMaterial extends Material {
 
 		super();
 
+		this.isShadowMaterial = true;
+
 		this.type = 'ShadowMaterial';
 
 		this.color = new Color( 0x000000 );
@@ -32,6 +34,4 @@ class ShadowMaterial extends Material {
 
 }
 
-ShadowMaterial.prototype.isShadowMaterial = true;
-
 export { ShadowMaterial };
diff --git a/src/materials/SpriteMaterial.js b/src/materials/SpriteMaterial.js
index 69751e98fce53..911e9abe75f37 100644
--- a/src/materials/SpriteMaterial.js
+++ b/src/materials/SpriteMaterial.js
@@ -7,6 +7,8 @@ class SpriteMaterial extends Material {
 
 		super();
 
+		this.isSpriteMaterial = true;
+
 		this.type = 'SpriteMaterial';
 
 		this.color = new Color( 0xffffff );
@@ -49,6 +51,4 @@ class SpriteMaterial extends Material {
 
 }
 
-SpriteMaterial.prototype.isSpriteMaterial = true;
-
 export { SpriteMaterial };
diff --git a/src/math/Box2.js b/src/math/Box2.js
index 02dcaa92f3ce5..7f47e104bf167 100644
--- a/src/math/Box2.js
+++ b/src/math/Box2.js
@@ -6,6 +6,8 @@ class Box2 {
 
 	constructor( min = new Vector2( + Infinity, + Infinity ), max = new Vector2( - Infinity, - Infinity ) ) {
 
+		this.isBox2 = true;
+
 		this.min = min;
 		this.max = max;
 
@@ -198,6 +200,4 @@ class Box2 {
 
 }
 
-Box2.prototype.isBox2 = true;
-
 export { Box2 };
diff --git a/src/math/Box3.js b/src/math/Box3.js
index eb52f57b37726..1110d1c219102 100644
--- a/src/math/Box3.js
+++ b/src/math/Box3.js
@@ -4,6 +4,8 @@ class Box3 {
 
 	constructor( min = new Vector3( + Infinity, + Infinity, + Infinity ), max = new Vector3( - Infinity, - Infinity, - Infinity ) ) {
 
+		this.isBox3 = true;
+
 		this.min = min;
 		this.max = max;
 
@@ -469,8 +471,6 @@ class Box3 {
 
 }
 
-Box3.prototype.isBox3 = true;
-
 const _points = [
 	/*@__PURE__*/ new Vector3(),
 	/*@__PURE__*/ new Vector3(),
diff --git a/src/math/Color.js b/src/math/Color.js
index cc17c0b1937b7..e2c45f974fd38 100644
--- a/src/math/Color.js
+++ b/src/math/Color.js
@@ -56,6 +56,8 @@ class Color {
 
 	constructor( r, g, b ) {
 
+		this.isColor = true;
+
 		this.r = 1;
 		this.g = 1;
 		this.b = 1;
@@ -610,6 +612,4 @@ class Color {
 
 Color.NAMES = _colorKeywords;
 
-Color.prototype.isColor = true;
-
 export { Color, SRGBToLinear };
diff --git a/src/math/Euler.js b/src/math/Euler.js
index 943923f830201..b7f8a971ab7b8 100644
--- a/src/math/Euler.js
+++ b/src/math/Euler.js
@@ -9,6 +9,8 @@ class Euler {
 
 	constructor( x = 0, y = 0, z = 0, order = Euler.DefaultOrder ) {
 
+		this.isEuler = true;
+
 		this._x = x;
 		this._y = y;
 		this._z = z;
@@ -316,8 +318,6 @@ class Euler {
 
 }
 
-Euler.prototype.isEuler = true;
-
 Euler.DefaultOrder = 'XYZ';
 Euler.RotationOrders = [ 'XYZ', 'YZX', 'ZXY', 'XZY', 'YXZ', 'ZYX' ];
 
diff --git a/src/math/Matrix3.js b/src/math/Matrix3.js
index 9005740e2f082..898522dfd6ae2 100644
--- a/src/math/Matrix3.js
+++ b/src/math/Matrix3.js
@@ -2,6 +2,8 @@ class Matrix3 {
 
 	constructor() {
 
+		this.isMatrix3 = true;
+
 		this.elements = [
 
 			1, 0, 0,
@@ -334,6 +336,4 @@ class Matrix3 {
 
 }
 
-Matrix3.prototype.isMatrix3 = true;
-
 export { Matrix3 };
diff --git a/src/math/Matrix4.js b/src/math/Matrix4.js
index 5383e24c3f9d9..2c327f35faacf 100644
--- a/src/math/Matrix4.js
+++ b/src/math/Matrix4.js
@@ -1,9 +1,10 @@
 import { Vector3 } from './Vector3.js';
-
 class Matrix4 {
 
 	constructor() {
 
+		this.isMatrix4 = true;
+
 		this.elements = [
 
 			1, 0, 0, 0,
@@ -872,8 +873,6 @@ class Matrix4 {
 
 }
 
-Matrix4.prototype.isMatrix4 = true;
-
 const _v1 = /*@__PURE__*/ new Vector3();
 const _m1 = /*@__PURE__*/ new Matrix4();
 const _zero = /*@__PURE__*/ new Vector3( 0, 0, 0 );
diff --git a/src/math/Plane.js b/src/math/Plane.js
index fc8a471b7e37f..795f9173f81cb 100644
--- a/src/math/Plane.js
+++ b/src/math/Plane.js
@@ -9,6 +9,8 @@ class Plane {
 
 	constructor( normal = new Vector3( 1, 0, 0 ), constant = 0 ) {
 
+		this.isPlane = true;
+
 		// normal is assumed to be normalized
 
 		this.normal = normal;
@@ -200,6 +202,4 @@ class Plane {
 
 }
 
-Plane.prototype.isPlane = true;
-
 export { Plane };
diff --git a/src/math/Quaternion.js b/src/math/Quaternion.js
index 2e998856384f6..6f38435266c1e 100644
--- a/src/math/Quaternion.js
+++ b/src/math/Quaternion.js
@@ -4,6 +4,8 @@ class Quaternion {
 
 	constructor( x = 0, y = 0, z = 0, w = 1 ) {
 
+		this.isQuaternion = true;
+
 		this._x = x;
 		this._y = y;
 		this._z = z;
@@ -693,6 +695,4 @@ class Quaternion {
 
 }
 
-Quaternion.prototype.isQuaternion = true;
-
 export { Quaternion };
diff --git a/src/math/SphericalHarmonics3.js b/src/math/SphericalHarmonics3.js
index 2d8796fba3a70..5ec3610534b07 100644
--- a/src/math/SphericalHarmonics3.js
+++ b/src/math/SphericalHarmonics3.js
@@ -14,6 +14,8 @@ class SphericalHarmonics3 {
 
 	constructor() {
 
+		this.isSphericalHarmonics3 = true;
+
 		this.coefficients = [];
 
 		for ( let i = 0; i < 9; i ++ ) {
@@ -238,6 +240,4 @@ class SphericalHarmonics3 {
 
 }
 
-SphericalHarmonics3.prototype.isSphericalHarmonics3 = true;
-
 export { SphericalHarmonics3 };
diff --git a/src/math/Vector2.js b/src/math/Vector2.js
index 88592aa34d087..8000533a7c1f3 100644
--- a/src/math/Vector2.js
+++ b/src/math/Vector2.js
@@ -2,6 +2,8 @@ class Vector2 {
 
 	constructor( x = 0, y = 0 ) {
 
+		this.isVector2 = true;
+
 		this.x = x;
 		this.y = y;
 
@@ -479,6 +481,4 @@ class Vector2 {
 
 }
 
-Vector2.prototype.isVector2 = true;
-
 export { Vector2 };
diff --git a/src/math/Vector3.js b/src/math/Vector3.js
index f88aa3e8feddf..8ab45747d6d8d 100644
--- a/src/math/Vector3.js
+++ b/src/math/Vector3.js
@@ -1,10 +1,11 @@
 import * as MathUtils from './MathUtils.js';
 import { Quaternion } from './Quaternion.js';
-
 class Vector3 {
 
 	constructor( x = 0, y = 0, z = 0 ) {
 
+		this.isVector3 = true;
+
 		this.x = x;
 		this.y = y;
 		this.z = z;
@@ -747,8 +748,6 @@ class Vector3 {
 
 }
 
-Vector3.prototype.isVector3 = true;
-
 const _vector = /*@__PURE__*/ new Vector3();
 const _quaternion = /*@__PURE__*/ new Quaternion();
 
diff --git a/src/math/Vector4.js b/src/math/Vector4.js
index c9af047ace0a1..d2edcf22df7db 100644
--- a/src/math/Vector4.js
+++ b/src/math/Vector4.js
@@ -2,6 +2,8 @@ class Vector4 {
 
 	constructor( x = 0, y = 0, z = 0, w = 1 ) {
 
+		this.isVector4 = true;
+
 		this.x = x;
 		this.y = y;
 		this.z = z;
@@ -659,6 +661,4 @@ class Vector4 {
 
 }
 
-Vector4.prototype.isVector4 = true;
-
 export { Vector4 };
diff --git a/src/objects/Bone.js b/src/objects/Bone.js
index 01d87b5fb944b..a673aab3725c2 100644
--- a/src/objects/Bone.js
+++ b/src/objects/Bone.js
@@ -6,12 +6,12 @@ class Bone extends Object3D {
 
 		super();
 
+		this.isBone = true;
+
 		this.type = 'Bone';
 
 	}
 
 }
 
-Bone.prototype.isBone = true;
-
 export { Bone };
diff --git a/src/objects/Group.js b/src/objects/Group.js
index 59a04edd45ec5..d4fee8425505f 100644
--- a/src/objects/Group.js
+++ b/src/objects/Group.js
@@ -6,12 +6,12 @@ class Group extends Object3D {
 
 		super();
 
+		this.isGroup = true;
+
 		this.type = 'Group';
 
 	}
 
 }
 
-Group.prototype.isGroup = true;
-
 export { Group };
diff --git a/src/objects/InstancedMesh.js b/src/objects/InstancedMesh.js
index ade4d60d7596f..b37dc2257cdf4 100644
--- a/src/objects/InstancedMesh.js
+++ b/src/objects/InstancedMesh.js
@@ -15,6 +15,8 @@ class InstancedMesh extends Mesh {
 
 		super( geometry, material );
 
+		this.isInstancedMesh = true;
+
 		this.instanceMatrix = new InstancedBufferAttribute( new Float32Array( count * 16 ), 16 );
 		this.instanceColor = null;
 
@@ -121,6 +123,4 @@ class InstancedMesh extends Mesh {
 
 }
 
-InstancedMesh.prototype.isInstancedMesh = true;
-
 export { InstancedMesh };
diff --git a/src/objects/Line.js b/src/objects/Line.js
index d2047c8c25a73..5ee17c2d65867 100644
--- a/src/objects/Line.js
+++ b/src/objects/Line.js
@@ -19,6 +19,8 @@ class Line extends Object3D {
 
 		super();
 
+		this.isLine = true;
+
 		this.type = 'Line';
 
 		this.geometry = geometry;
@@ -247,7 +249,4 @@ class Line extends Object3D {
 
 }
 
-Line.prototype.isLine = true;
-
-
 export { Line };
diff --git a/src/objects/LineLoop.js b/src/objects/LineLoop.js
index aa34882084590..8c3ac94fee7c3 100644
--- a/src/objects/LineLoop.js
+++ b/src/objects/LineLoop.js
@@ -6,12 +6,12 @@ class LineLoop extends Line {
 
 		super( geometry, material );
 
+		this.isLineLoop = true;
+
 		this.type = 'LineLoop';
 
 	}
 
 }
 
-LineLoop.prototype.isLineLoop = true;
-
 export { LineLoop };
diff --git a/src/objects/LineSegments.js b/src/objects/LineSegments.js
index 5e06c7954a18c..b28d3661f022e 100644
--- a/src/objects/LineSegments.js
+++ b/src/objects/LineSegments.js
@@ -11,6 +11,8 @@ class LineSegments extends Line {
 
 		super( geometry, material );
 
+		this.isLineSegments = true;
+
 		this.type = 'LineSegments';
 
 	}
@@ -58,6 +60,4 @@ class LineSegments extends Line {
 
 }
 
-LineSegments.prototype.isLineSegments = true;
-
 export { LineSegments };
diff --git a/src/objects/Mesh.js b/src/objects/Mesh.js
index fccbb035698a0..973dc10c2e1f3 100644
--- a/src/objects/Mesh.js
+++ b/src/objects/Mesh.js
@@ -38,6 +38,8 @@ class Mesh extends Object3D {
 
 		super();
 
+		this.isMesh = true;
+
 		this.type = 'Mesh';
 
 		this.geometry = geometry;
@@ -286,8 +288,6 @@ class Mesh extends Object3D {
 
 }
 
-Mesh.prototype.isMesh = true;
-
 function checkIntersection( object, material, raycaster, ray, pA, pB, pC, point ) {
 
 	let intersect;
diff --git a/src/objects/Points.js b/src/objects/Points.js
index b25f38fb39fbd..61be0e6a4c57a 100644
--- a/src/objects/Points.js
+++ b/src/objects/Points.js
@@ -17,6 +17,8 @@ class Points extends Object3D {
 
 		super();
 
+		this.isPoints = true;
+
 		this.type = 'Points';
 
 		this.geometry = geometry;
@@ -153,8 +155,6 @@ class Points extends Object3D {
 
 }
 
-Points.prototype.isPoints = true;
-
 function testPoint( point, index, localThresholdSq, matrixWorld, raycaster, intersects, object ) {
 
 	const rayPointDistanceSq = _ray.distanceSqToPoint( point );
diff --git a/src/objects/SkinnedMesh.js b/src/objects/SkinnedMesh.js
index eabba0d1111a2..602d1caa14750 100644
--- a/src/objects/SkinnedMesh.js
+++ b/src/objects/SkinnedMesh.js
@@ -17,6 +17,8 @@ class SkinnedMesh extends Mesh {
 
 		super( geometry, material );
 
+		this.isSkinnedMesh = true;
+
 		this.type = 'SkinnedMesh';
 
 		this.bindMode = 'attached';
@@ -146,6 +148,4 @@ class SkinnedMesh extends Mesh {
 
 }
 
-SkinnedMesh.prototype.isSkinnedMesh = true;
-
 export { SkinnedMesh };
diff --git a/src/objects/Sprite.js b/src/objects/Sprite.js
index 93564674adbb7..39d69d4a68e11 100644
--- a/src/objects/Sprite.js
+++ b/src/objects/Sprite.js
@@ -32,6 +32,8 @@ class Sprite extends Object3D {
 
 		super();
 
+		this.isSprite = true;
+
 		this.type = 'Sprite';
 
 		if ( _geometry === undefined ) {
@@ -149,8 +151,6 @@ class Sprite extends Object3D {
 
 }
 
-Sprite.prototype.isSprite = true;
-
 function transformVertex( vertexPosition, mvPosition, center, scale, sin, cos ) {
 
 	// compute position in camera space
diff --git a/src/renderers/WebGL3DRenderTarget.js b/src/renderers/WebGL3DRenderTarget.js
index 6c9e6a0a1f63a..5b78f42bc2ce0 100644
--- a/src/renderers/WebGL3DRenderTarget.js
+++ b/src/renderers/WebGL3DRenderTarget.js
@@ -7,6 +7,8 @@ class WebGL3DRenderTarget extends WebGLRenderTarget {
 
 		super( width, height );
 
+		this.isWebGL3DRenderTarget = true;
+
 		this.depth = depth;
 
 		this.texture = new Data3DTexture( null, width, height, depth );
@@ -17,6 +19,4 @@ class WebGL3DRenderTarget extends WebGLRenderTarget {
 
 }
 
-WebGL3DRenderTarget.prototype.isWebGL3DRenderTarget = true;
-
 export { WebGL3DRenderTarget };
diff --git a/src/renderers/WebGLArrayRenderTarget.js b/src/renderers/WebGLArrayRenderTarget.js
index 754a52a58804b..4f63411383b36 100644
--- a/src/renderers/WebGLArrayRenderTarget.js
+++ b/src/renderers/WebGLArrayRenderTarget.js
@@ -7,6 +7,8 @@ class WebGLArrayRenderTarget extends WebGLRenderTarget {
 
 		super( width, height );
 
+		this.isWebGLArrayRenderTarget = true;
+
 		this.depth = depth;
 
 		this.texture = new DataArrayTexture( null, width, height, depth );
@@ -17,6 +19,4 @@ class WebGLArrayRenderTarget extends WebGLRenderTarget {
 
 }
 
-WebGLArrayRenderTarget.prototype.isWebGLArrayRenderTarget = true;
-
 export { WebGLArrayRenderTarget };
diff --git a/src/renderers/WebGLCubeRenderTarget.js b/src/renderers/WebGLCubeRenderTarget.js
index 1e5fd1f6d8e11..a5a7dddc22f05 100644
--- a/src/renderers/WebGLCubeRenderTarget.js
+++ b/src/renderers/WebGLCubeRenderTarget.js
@@ -13,6 +13,8 @@ class WebGLCubeRenderTarget extends WebGLRenderTarget {
 
 		super( size, size, options );
 
+		this.isWebGLCubeRenderTarget = true;
+
 		const image = { width: size, height: size, depth: 1 };
 		const images = [ image, image, image, image, image, image ];
 
@@ -141,6 +143,4 @@ class WebGLCubeRenderTarget extends WebGLRenderTarget {
 
 }
 
-WebGLCubeRenderTarget.prototype.isWebGLCubeRenderTarget = true;
-
 export { WebGLCubeRenderTarget };
diff --git a/src/renderers/WebGLMultipleRenderTargets.js b/src/renderers/WebGLMultipleRenderTargets.js
index a0bff130049bf..01613215e95d5 100644
--- a/src/renderers/WebGLMultipleRenderTargets.js
+++ b/src/renderers/WebGLMultipleRenderTargets.js
@@ -6,6 +6,8 @@ class WebGLMultipleRenderTargets extends WebGLRenderTarget {
 
 		super( width, height, options );
 
+		this.isWebGLMultipleRenderTargets = true;
+
 		const texture = this.texture;
 
 		this.texture = [];
@@ -77,6 +79,4 @@ class WebGLMultipleRenderTargets extends WebGLRenderTarget {
 
 }
 
-WebGLMultipleRenderTargets.prototype.isWebGLMultipleRenderTargets = true;
-
 export { WebGLMultipleRenderTargets };
diff --git a/src/renderers/WebGLRenderTarget.js b/src/renderers/WebGLRenderTarget.js
index e286d2ccd66ce..346dc092aedf6 100644
--- a/src/renderers/WebGLRenderTarget.js
+++ b/src/renderers/WebGLRenderTarget.js
@@ -15,6 +15,8 @@ class WebGLRenderTarget extends EventDispatcher {
 
 		super();
 
+		this.isWebGLRenderTarget = true;
+
 		this.width = width;
 		this.height = height;
 		this.depth = 1;
@@ -105,6 +107,4 @@ class WebGLRenderTarget extends EventDispatcher {
 
 }
 
-WebGLRenderTarget.prototype.isWebGLRenderTarget = true;
-
 export { WebGLRenderTarget };
diff --git a/src/renderers/WebGLRenderer.js b/src/renderers/WebGLRenderer.js
index cbd21455882aa..696d68a47266f 100644
--- a/src/renderers/WebGLRenderer.js
+++ b/src/renderers/WebGLRenderer.js
@@ -56,6 +56,8 @@ function createCanvasElement() {
 
 function WebGLRenderer( parameters = {} ) {
 
+	this.isWebGLRenderer = true;
+
 	const _canvas = parameters.canvas !== undefined ? parameters.canvas : createCanvasElement(),
 		_context = parameters.context !== undefined ? parameters.context : null,
 
@@ -2191,6 +2193,4 @@ function WebGLRenderer( parameters = {} ) {
 
 }
 
-WebGLRenderer.prototype.isWebGLRenderer = true;
-
 export { WebGLRenderer };
diff --git a/src/scenes/Fog.js b/src/scenes/Fog.js
index ccd4bd706fc7d..03b89c71d824a 100644
--- a/src/scenes/Fog.js
+++ b/src/scenes/Fog.js
@@ -4,6 +4,8 @@ class Fog {
 
 	constructor( color, near = 1, far = 1000 ) {
 
+		this.isFog = true;
+
 		this.name = '';
 
 		this.color = new Color( color );
@@ -32,6 +34,4 @@ class Fog {
 
 }
 
-Fog.prototype.isFog = true;
-
 export { Fog };
diff --git a/src/scenes/FogExp2.js b/src/scenes/FogExp2.js
index 9cb28290866a5..3f60d0881e25c 100644
--- a/src/scenes/FogExp2.js
+++ b/src/scenes/FogExp2.js
@@ -4,6 +4,8 @@ class FogExp2 {
 
 	constructor( color, density = 0.00025 ) {
 
+		this.isFogExp2 = true;
+
 		this.name = '';
 
 		this.color = new Color( color );
@@ -29,6 +31,4 @@ class FogExp2 {
 
 }
 
-FogExp2.prototype.isFogExp2 = true;
-
 export { FogExp2 };
diff --git a/src/scenes/Scene.js b/src/scenes/Scene.js
index 2ca0ec5554cd8..2dc6785cb9d8b 100644
--- a/src/scenes/Scene.js
+++ b/src/scenes/Scene.js
@@ -6,6 +6,8 @@ class Scene extends Object3D {
 
 		super();
 
+		this.isScene = true;
+
 		this.type = 'Scene';
 
 		this.background = null;
@@ -53,6 +55,4 @@ class Scene extends Object3D {
 
 }
 
-Scene.prototype.isScene = true;
-
 export { Scene };
diff --git a/src/textures/CanvasTexture.js b/src/textures/CanvasTexture.js
index 35511ff133c82..61a58b3b34929 100644
--- a/src/textures/CanvasTexture.js
+++ b/src/textures/CanvasTexture.js
@@ -6,12 +6,12 @@ class CanvasTexture extends Texture {
 
 		super( canvas, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy );
 
+		this.isCanvasTexture = true;
+
 		this.needsUpdate = true;
 
 	}
 
 }
 
-CanvasTexture.prototype.isCanvasTexture = true;
-
 export { CanvasTexture };
diff --git a/src/textures/CompressedTexture.js b/src/textures/CompressedTexture.js
index cf0e37d017bd2..319a674da5f31 100644
--- a/src/textures/CompressedTexture.js
+++ b/src/textures/CompressedTexture.js
@@ -6,6 +6,8 @@ class CompressedTexture extends Texture {
 
 		super( null, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy, encoding );
 
+		this.isCompressedTexture = true;
+
 		this.image = { width: width, height: height };
 		this.mipmaps = mipmaps;
 
@@ -23,6 +25,4 @@ class CompressedTexture extends Texture {
 
 }
 
-CompressedTexture.prototype.isCompressedTexture = true;
-
 export { CompressedTexture };
diff --git a/src/textures/CubeTexture.js b/src/textures/CubeTexture.js
index 84db191d0bdbd..0489f8225ab52 100644
--- a/src/textures/CubeTexture.js
+++ b/src/textures/CubeTexture.js
@@ -10,6 +10,8 @@ class CubeTexture extends Texture {
 
 		super( images, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy, encoding );
 
+		this.isCubeTexture = true;
+
 		this.flipY = false;
 
 	}
@@ -28,6 +30,4 @@ class CubeTexture extends Texture {
 
 }
 
-CubeTexture.prototype.isCubeTexture = true;
-
 export { CubeTexture };
diff --git a/src/textures/Data3DTexture.js b/src/textures/Data3DTexture.js
index 763c058189119..36348cc1f04a1 100644
--- a/src/textures/Data3DTexture.js
+++ b/src/textures/Data3DTexture.js
@@ -15,6 +15,8 @@ class Data3DTexture extends Texture {
 
 		super( null );
 
+		this.isData3DTexture = true;
+
 		this.image = { data, width, height, depth };
 
 		this.magFilter = NearestFilter;
@@ -30,6 +32,4 @@ class Data3DTexture extends Texture {
 
 }
 
-Data3DTexture.prototype.isData3DTexture = true;
-
 export { Data3DTexture };
diff --git a/src/textures/DataArrayTexture.js b/src/textures/DataArrayTexture.js
index 72badd78b5712..759973df66378 100644
--- a/src/textures/DataArrayTexture.js
+++ b/src/textures/DataArrayTexture.js
@@ -7,6 +7,8 @@ class DataArrayTexture extends Texture {
 
 		super( null );
 
+		this.isDataArrayTexture = true;
+
 		this.image = { data, width, height, depth };
 
 		this.magFilter = NearestFilter;
@@ -22,6 +24,4 @@ class DataArrayTexture extends Texture {
 
 }
 
-DataArrayTexture.prototype.isDataArrayTexture = true;
-
 export { DataArrayTexture };
diff --git a/src/textures/DataTexture.js b/src/textures/DataTexture.js
index 3aabd2cc74e6a..9cefb13dc7b5d 100644
--- a/src/textures/DataTexture.js
+++ b/src/textures/DataTexture.js
@@ -7,6 +7,8 @@ class DataTexture extends Texture {
 
 		super( null, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy, encoding );
 
+		this.isDataTexture = true;
+
 		this.image = { data: data, width: width, height: height };
 
 		this.generateMipmaps = false;
@@ -17,6 +19,4 @@ class DataTexture extends Texture {
 
 }
 
-DataTexture.prototype.isDataTexture = true;
-
 export { DataTexture };
diff --git a/src/textures/DepthTexture.js b/src/textures/DepthTexture.js
index 79cb16e3c02c2..fba1630fd3326 100644
--- a/src/textures/DepthTexture.js
+++ b/src/textures/DepthTexture.js
@@ -18,6 +18,8 @@ class DepthTexture extends Texture {
 
 		super( null, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy );
 
+		this.isDepthTexture = true;
+
 		this.image = { width: width, height: height };
 
 		this.magFilter = magFilter !== undefined ? magFilter : NearestFilter;
@@ -31,6 +33,4 @@ class DepthTexture extends Texture {
 
 }
 
-DepthTexture.prototype.isDepthTexture = true;
-
 export { DepthTexture };
diff --git a/src/textures/FramebufferTexture.js b/src/textures/FramebufferTexture.js
index 3a8beb74c5dc2..322d74031c7ad 100644
--- a/src/textures/FramebufferTexture.js
+++ b/src/textures/FramebufferTexture.js
@@ -7,6 +7,8 @@ class FramebufferTexture extends Texture {
 
 		super( { width, height } );
 
+		this.isFramebufferTexture = true;
+
 		this.format = format;
 
 		this.magFilter = NearestFilter;
@@ -20,6 +22,4 @@ class FramebufferTexture extends Texture {
 
 }
 
-FramebufferTexture.prototype.isFramebufferTexture = true;
-
 export { FramebufferTexture };
diff --git a/src/textures/Source.js b/src/textures/Source.js
index d17fab91856ac..659a1c74eb45e 100644
--- a/src/textures/Source.js
+++ b/src/textures/Source.js
@@ -5,6 +5,8 @@ class Source {
 
 	constructor( data = null ) {
 
+		this.isSource = true;
+
 		this.uuid = MathUtils.generateUUID();
 
 		this.data = data;
@@ -118,6 +120,4 @@ function serializeImage( image ) {
 
 }
 
-Source.prototype.isSource = true;
-
 export { Source };
diff --git a/src/textures/Texture.js b/src/textures/Texture.js
index b03e055b69a65..b552e32062524 100644
--- a/src/textures/Texture.js
+++ b/src/textures/Texture.js
@@ -23,6 +23,8 @@ class Texture extends EventDispatcher {
 
 		super();
 
+		this.isTexture = true;
+
 		Object.defineProperty( this, 'id', { value: textureId ++ } );
 
 		this.uuid = MathUtils.generateUUID();
@@ -303,6 +305,4 @@ class Texture extends EventDispatcher {
 Texture.DEFAULT_IMAGE = null;
 Texture.DEFAULT_MAPPING = UVMapping;
 
-Texture.prototype.isTexture = true;
-
 export { Texture };
diff --git a/src/textures/VideoTexture.js b/src/textures/VideoTexture.js
index b49d397cd87d1..9f6b7123513e5 100644
--- a/src/textures/VideoTexture.js
+++ b/src/textures/VideoTexture.js
@@ -7,6 +7,8 @@ class VideoTexture extends Texture {
 
 		super( video, mapping, wrapS, wrapT, magFilter, minFilter, format, type, anisotropy );
 
+		this.isVideoTexture = true;
+
 		this.minFilter = minFilter !== undefined ? minFilter : LinearFilter;
 		this.magFilter = magFilter !== undefined ? magFilter : LinearFilter;
 
@@ -50,6 +52,4 @@ class VideoTexture extends Texture {
 
 }
 
-VideoTexture.prototype.isVideoTexture = true;
-
 export { VideoTexture };
diff --git a/test/unit/src/core/Object3D.tests.js b/test/unit/src/core/Object3D.tests.js
index d500bb97dc9e2..a5330cb197166 100644
--- a/test/unit/src/core/Object3D.tests.js
+++ b/test/unit/src/core/Object3D.tests.js
@@ -301,11 +301,9 @@ export default QUnit.module( 'Core', () => {
 			obj.translateOnAxis( new Vector3( 0, 1, 0 ), 1.23 );
 			obj.translateOnAxis( new Vector3( 0, 0, 1 ), - 4.56 );
 
-			assert.propEqual( obj.position, {
-				x: 1,
-				y: 1.23,
-				z: - 4.56
-			} );
+			assert.numEqual( obj.position.x, 1, 'x is equal' );
+			assert.numEqual( obj.position.y, 1.23, 'y is equal' );
+			assert.numEqual( obj.position.z, - 4.56, 'z is equal' );
 
 		} );