mirror of
https://github.com/idanoo/GoScrobble.git
synced 2024-11-22 16:35:14 +00:00
88 lines
3.2 KiB
JavaScript
88 lines
3.2 KiB
JavaScript
// 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])
|
|
);
|