Ignore non js identifiers

.eslintrc.yml

@@ -1 +1,3 @@
 extends: standard
+env:
+  mocha: true

package.json

@@ -47,15 +47,15 @@
     "eslint-plugin-node": "^8.0.0",
     "eslint-plugin-promise": "^4.0.1",
     "eslint-plugin-standard": "^4.0.0",
-    "karma": "^3.1.4",
+    "karma": "^4.0.0",
     "karma-chrome-launcher": "^2.0.0",
     "karma-coverage": "^1.1.1",
     "karma-firefox-launcher": "^1.0.0",
     "karma-mocha": "^1.3.0",
     "karma-sourcemap-loader": "^0.3.7",
     "karma-spec-reporter": "~0.0.32",
     "karma-webpack": "^3.0.5",
-    "mocha": "^5.2.0",
+    "mocha": "^6.0.2",
     "nyc": "^13.1.0",
     "rimraf": "^2.5.4",
     "webpack": "^4.28.3",

src/common.js

@@ -8,6 +8,11 @@ exports.hasWindow = hasWindow
 const hasGlobal = (typeof global !== 'undefined')
 exports.hasGlobal = hasGlobal
 
+const NON_IDENTIFIER = /^\d|-|^(break|case|catch|continue|debugger|default|delete|do|else|finally|for|function|if|in|instanceof|new|return|switch|this|throw|try|typeof|var|void|while|with|class|const|enum|export|extends|import|super|implements|interface|let|package|private|protected|public|static|yield|null|true|false)$/
+
+const isIdentifier = key => !NON_IDENTIFIER.test(key)
+exports.isIdentifier = isIdentifier
+
 /**
 * create a fresh context where nearly nothing is allowed
 * @private
@@ -28,20 +33,23 @@ exports.createContext = function () {
     Function: undefined
   }
 
+  const fillContext = (root) => {
+    Object.keys(root).forEach(key => {
+      if (isIdentifier(key)) {
+        context[key] = undefined
+      }
+    })
+  }
+
   // locally define all potential global vars
   if (hasGlobal) {
-    Object.keys(global).forEach(function (key) {
-      context[key] = undefined
-    })
+    fillContext(global)
     cloneFunctions(context)
     context.Buffer = _protect('Buffer')
     context.console = clones(console, console) // console needs special treatment
   }
   if (hasWindow) {
-    Object.keys(window).forEach(function (key) {
-      context[key] = undefined
-    })
-
+    fillContext(window, true)
     cloneFunctions(context)
     protectBuiltInObjects(context)
     context.console = clones(console, console) // console needs special treatment
@@ -56,8 +64,10 @@ exports.createContext = function () {
 * @private
 */
 exports.allow = function (context, newContext) {
-  Object.keys(context || {}).forEach(function (key) {
-    newContext[key] = context[key] // this is harmful - objects can be overwritten
+  Object.keys(context || {}).forEach(key => {
+    if (isIdentifier(key)) {
+      newContext[key] = context[key] // this is harmful - objects can be overwritten
+    }
   })
 }