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node_modules/es6-symbol/polyfill.js
| 87 lines
| 3.2 KiB
| application/javascript
| JavascriptLexer
|
| r789 | // ES2015 Symbol polyfill for environments that do not (or partially) support it | |||
| "use strict"; | ||||
| var d = require("d") | ||||
| , validateSymbol = require("./validate-symbol") | ||||
| , NativeSymbol = require("ext/global-this").Symbol | ||||
| , generateName = require("./lib/private/generate-name") | ||||
| , setupStandardSymbols = require("./lib/private/setup/standard-symbols") | ||||
| , setupSymbolRegistry = require("./lib/private/setup/symbol-registry"); | ||||
| var create = Object.create | ||||
| , defineProperties = Object.defineProperties | ||||
| , defineProperty = Object.defineProperty; | ||||
| var SymbolPolyfill, HiddenSymbol, isNativeSafe; | ||||
| if (typeof NativeSymbol === "function") { | ||||
| try { | ||||
| String(NativeSymbol()); | ||||
| isNativeSafe = true; | ||||
| } catch (ignore) {} | ||||
| } else { | ||||
| NativeSymbol = null; | ||||
| } | ||||
| // 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) { | ||||
| if (this instanceof HiddenSymbol) throw new TypeError("Symbol is not a constructor"); | ||||
| return SymbolPolyfill(description); | ||||
| }; | ||||
| // Exposed `Symbol` constructor | ||||
| // (returns instances of HiddenSymbol) | ||||
| module.exports = SymbolPolyfill = function Symbol(description) { | ||||
| var symbol; | ||||
| if (this instanceof Symbol) throw new TypeError("Symbol is not a constructor"); | ||||
| if (isNativeSafe) return NativeSymbol(description); | ||||
| symbol = create(HiddenSymbol.prototype); | ||||
| description = description === undefined ? "" : String(description); | ||||
| return defineProperties(symbol, { | ||||
| __description__: d("", description), | ||||
| __name__: d("", generateName(description)) | ||||
| }); | ||||
| }; | ||||
| setupStandardSymbols(SymbolPolyfill); | ||||
| setupSymbolRegistry(SymbolPolyfill); | ||||
| // Internal tweaks for real symbol producer | ||||
| defineProperties(HiddenSymbol.prototype, { | ||||
| constructor: d(SymbolPolyfill), | ||||
| toString: d("", function () { return this.__name__; }) | ||||
| }); | ||||
| // 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, { | ||||
| toString: d(function () { return "Symbol (" + validateSymbol(this).__description__ + ")"; }), | ||||
| valueOf: d(function () { return validateSymbol(this); }) | ||||
| }); | ||||
| defineProperty( | ||||
| SymbolPolyfill.prototype, | ||||
| SymbolPolyfill.toPrimitive, | ||||
| d("", function () { | ||||
| var symbol = validateSymbol(this); | ||||
| if (typeof symbol === "symbol") return symbol; | ||||
| return symbol.toString(); | ||||
| }) | ||||
| ); | ||||
| defineProperty(SymbolPolyfill.prototype, SymbolPolyfill.toStringTag, d("c", "Symbol")); | ||||
| // 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]) | ||||
| ); | ||||