diff options
author | Florian Dold <florian.dold@gmail.com> | 2017-08-14 05:01:11 +0200 |
---|---|---|
committer | Florian Dold <florian.dold@gmail.com> | 2017-08-14 05:02:09 +0200 |
commit | 363723fc84f7b8477592e0105aeb331ec9a017af (patch) | |
tree | 29f92724f34131bac64d6a318dd7e30612e631c7 /node_modules/es6-symbol/polyfill.js | |
parent | 5634e77ad96bfe1818f6b6ee70b7379652e5487f (diff) |
node_modules
Diffstat (limited to 'node_modules/es6-symbol/polyfill.js')
-rw-r--r-- | node_modules/es6-symbol/polyfill.js | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/node_modules/es6-symbol/polyfill.js b/node_modules/es6-symbol/polyfill.js new file mode 100644 index 000000000..dca879a3e --- /dev/null +++ b/node_modules/es6-symbol/polyfill.js @@ -0,0 +1,118 @@ +// ES2015 Symbol polyfill for environments that do not (or partially) support it + +'use strict'; + +var d = require('d') + , validateSymbol = require('./validate-symbol') + + , create = Object.create, defineProperties = Object.defineProperties + , defineProperty = Object.defineProperty, objPrototype = Object.prototype + , NativeSymbol, SymbolPolyfill, HiddenSymbol, globalSymbols = create(null) + , isNativeSafe; + +if (typeof Symbol === 'function') { + NativeSymbol = Symbol; + try { + String(NativeSymbol()); + isNativeSafe = true; + } catch (ignore) {} +} + +var generateName = (function () { + var created = create(null); + return function (desc) { + var postfix = 0, name, ie11BugWorkaround; + while (created[desc + (postfix || '')]) ++postfix; + desc += (postfix || ''); + created[desc] = true; + name = '@@' + desc; + defineProperty(objPrototype, name, d.gs(null, function (value) { + // For IE11 issue see: + // https://connect.microsoft.com/IE/feedbackdetail/view/1928508/ + // ie11-broken-getters-on-dom-objects + // https://github.com/medikoo/es6-symbol/issues/12 + if (ie11BugWorkaround) return; + ie11BugWorkaround = true; + defineProperty(this, name, d(value)); + ie11BugWorkaround = false; + })); + return name; + }; +}()); + +// 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)) + }); +}; +defineProperties(SymbolPolyfill, { + for: d(function (key) { + if (globalSymbols[key]) return globalSymbols[key]; + return (globalSymbols[key] = SymbolPolyfill(String(key))); + }), + keyFor: d(function (s) { + var key; + validateSymbol(s); + for (key in globalSymbols) if (globalSymbols[key] === s) return key; + }), + + // To ensure proper interoperability with other native functions (e.g. Array.from) + // fallback to eventual native implementation of given symbol + hasInstance: d('', (NativeSymbol && NativeSymbol.hasInstance) || SymbolPolyfill('hasInstance')), + isConcatSpreadable: d('', (NativeSymbol && NativeSymbol.isConcatSpreadable) || + SymbolPolyfill('isConcatSpreadable')), + iterator: d('', (NativeSymbol && NativeSymbol.iterator) || SymbolPolyfill('iterator')), + match: d('', (NativeSymbol && NativeSymbol.match) || SymbolPolyfill('match')), + replace: d('', (NativeSymbol && NativeSymbol.replace) || SymbolPolyfill('replace')), + search: d('', (NativeSymbol && NativeSymbol.search) || SymbolPolyfill('search')), + species: d('', (NativeSymbol && NativeSymbol.species) || SymbolPolyfill('species')), + split: d('', (NativeSymbol && NativeSymbol.split) || SymbolPolyfill('split')), + toPrimitive: d('', (NativeSymbol && NativeSymbol.toPrimitive) || SymbolPolyfill('toPrimitive')), + toStringTag: d('', (NativeSymbol && NativeSymbol.toStringTag) || SymbolPolyfill('toStringTag')), + unscopables: d('', (NativeSymbol && NativeSymbol.unscopables) || SymbolPolyfill('unscopables')) +}); + +// 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])); |