es6-symbol - npm Package Compare versions

Comparing version 3.0.1 to 3.0.2

package.json

 {
   "name": "es6-symbol",
-  "version": "3.0.1",
+  "version": "3.0.2",
   "description": "ECMAScript 6 Symbol polyfill",
@@ -22,3 +22,3 @@ "author": "Mariusz Nowak <[e-mail]> (http://www.medikoo.com/)",
     "d": "~0.1.1",
-    "es5-ext": "~0.10.8"
+    "es5-ext": "~0.10.10"
   },
@@ -25,0 +25,0 @@ "devDependencies": {

polyfill.js

@@ -0,1 +1,3 @@
+// ES2015 Symbol polyfill for environments that do not support it (or partially support it_
+
 'use strict';
@@ -34,2 +36,4 @@
 
+// Internal constructor (not one exposed) for creating Symbol instances.
+// This one is used to ensure that `someSymbol instanceof Symbol` always return false
 HiddenSymbol = function Symbol(description) {
@@ -39,2 +43,5 @@ if (this instanceof HiddenSymbol) throw new TypeError('TypeError: Symbol is not a constructor');
 };
+
+// Exposed `Symbol` constructor
+// (returns instances of HiddenSymbol)
 module.exports = SymbolPolyfill = function Symbol(description) {
@@ -60,2 +67,5 @@ var symbol;
 	}),
+
+	// If there's native implementation of given symbol, let's fallback to it
+	// to ensure proper interoperability with other native functions e.g. Array.from
 	hasInstance: d('', (NativeSymbol && NativeSymbol.hasInstance) || SymbolPolyfill('hasInstance')),
@@ -74,2 +84,4 @@ isConcatSpreadable: d('', (NativeSymbol && NativeSymbol.isConcatSpreadable) ||
 });
+
+// Internal tweaks for real symbol producer
 defineProperties(HiddenSymbol.prototype, {
@@ -80,2 +92,4 @@ constructor: d(SymbolPolyfill),
 
+// Proper implementation of methods exposed on Symbol.prototype
+// They won't be accessible on produced symbol instances as they derive from HiddenSymbol.prototype
 defineProperties(SymbolPolyfill.prototype, {
@@ -89,5 +103,11 @@ toString: d(function () { return 'Symbol (' + validateSymbol(this).__description__ + ')'; }),
 
+// Proper implementaton of toPrimitive and toStringTag for returned symbol instances
+defineProperty(HiddenSymbol.prototype, SymbolPolyfill.toStringTag,
+	d('c', SymbolPolyfill.prototype[SymbolPolyfill.toStringTag]));
+
+// Note: It's important to define `toPrimitive` as last one, as some implementations
+// implement `toPrimitive` natively without implementing `toStringTag` (or other specified symbols)
+// And that may invoke error in definition flow:
+// See: https://github.com/medikoo/es6-symbol/issues/13#issuecomment-164146149
 defineProperty(HiddenSymbol.prototype, SymbolPolyfill.toPrimitive,
 	d('c', SymbolPolyfill.prototype[SymbolPolyfill.toPrimitive]));
-defineProperty(HiddenSymbol.prototype, SymbolPolyfill.toStringTag,
-	d('c', SymbolPolyfill.prototype[SymbolPolyfill.toStringTag]));

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Improved metrics

Total package byte prevSize

14868

increased by9.08%

Lines of code

212

increased by7.61%

Dependency changes

• Updatedes5-ext@~0.10.10