73 lines
1.9 KiB
JavaScript
73 lines
1.9 KiB
JavaScript
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"use strict";
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/* global self, window, module, global, require */
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module.exports = function () {
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"use strict";
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var globalObject = void 0;
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function isFunction(x) {
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return typeof x === "function";
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}
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// Seek the global object
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if (global !== undefined) {
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globalObject = global;
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} else if (window !== undefined && window.document) {
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globalObject = window;
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} else {
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globalObject = self;
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}
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// Test for any native promise implementation, and if that
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// implementation appears to conform to the specificaton.
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// This code mostly nicked from the es6-promise module polyfill
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// and then fooled with.
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var hasPromiseSupport = function () {
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// No promise object at all, and it's a non-starter
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if (!globalObject.hasOwnProperty("Promise")) {
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return false;
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}
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// There is a Promise object. Does it conform to the spec?
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var P = globalObject.Promise;
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// Some of these methods are missing from
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// Firefox/Chrome experimental implementations
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if (!P.hasOwnProperty("resolve") || !P.hasOwnProperty("reject")) {
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return false;
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}
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if (!P.hasOwnProperty("all") || !P.hasOwnProperty("race")) {
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return false;
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}
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// Older version of the spec had a resolver object
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// as the arg rather than a function
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return function () {
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var resolve = void 0;
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var p = new globalObject.Promise(function (r) {
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resolve = r;
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});
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if (p) {
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return isFunction(resolve);
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}
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return false;
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}();
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}();
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// Export the native Promise implementation if it
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// looks like it matches the spec
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if (hasPromiseSupport) {
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return globalObject.Promise;
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}
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// Otherwise, return the es6-promise polyfill by @jaffathecake.
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return require("es6-promise").Promise;
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}();
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