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38 lines
858 B
38 lines
858 B
"use strict"; |
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var isFunction = require("../function/is-function"); |
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module.exports = function (executor) { |
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var Constructor; |
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if (isFunction(this)) { |
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Constructor = this; |
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} else if (typeof Promise === "function") { |
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Constructor = Promise; |
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} else { |
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throw new TypeError("Could not resolve Promise constuctor"); |
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} |
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var lazyThen; |
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var promise = new Constructor(function (resolve, reject) { |
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lazyThen = function (onSuccess, onFailure) { |
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if (!hasOwnProperty.call(this, "then")) { |
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// Sanity check |
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throw new Error("Unexpected (inherited) lazy then invocation"); |
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} |
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try { |
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executor(resolve, reject); |
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} catch (reason) { |
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reject(reason); |
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} |
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delete this.then; |
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return this.then(onSuccess, onFailure); |
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}; |
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}); |
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return Object.defineProperty(promise, "then", { |
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configurable: true, |
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writable: true, |
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value: lazyThen |
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}); |
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};
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