Update: improve use-isnan rule to detect Number.NaN (fixes #14715)

docs/rules/use-isnan.md

@@ -25,6 +25,14 @@ if (foo == NaN) {
 if (foo != NaN) {
     // ...
 }
+
+if (foo == Number.NaN) {
+    // ...
+}
+
+if (foo != Number.NaN) {
+    // ...
+}
 ```
 
 Examples of **correct** code for this rule:
@@ -77,6 +85,26 @@ switch (NaN) {
         break;
     // ...
 }
+
+switch (foo) {
+    case Number.NaN:
+        bar();
+        break;
+    case 1:
+        baz();
+        break;
+    // ...
+}
+
+switch (Number.NaN) {
+    case a:
+        bar();
+        break;
+    case b:
+        baz();
+        break;
+    // ...
+}
 ```
 
 Examples of **correct** code for this rule with `"enforceForSwitchCase"` option set to `true` (default):
@@ -126,6 +154,25 @@ switch (NaN) {
         break;
     // ...
 }
+
+switch (foo) {
+    case Number.NaN:
+        bar();
+        break;
+    case 1:
+        baz();
+        break;
+    // ...
+}
+
+switch (Number.NaN) {
+    case a:
+        bar();
+        break;
+    case b:
+        baz();
+        break;
+    /
 ```
 
 ### enforceForIndexOf

lib/rules/use-isnan.js

@@ -21,7 +21,10 @@ const astUtils = require("./utils/ast-utils");
  * @returns {boolean} `true` if the node is 'NaN' identifier.
  */
 function isNaNIdentifier(node) {
-    return Boolean(node) && node.type === "Identifier" && node.name === "NaN";
+    return Boolean(node) && (node.type === "Identifier" && node.name === "NaN" ||
+        (node.type === "MemberExpression" &&
+        node.object.type === "Identifier" && node.object.name === "Number" &&
+        node.property.type === "Identifier" && node.property.name === "NaN"));
 }
 
 //------------------------------------------------------------------------------