28 lines
884 B
Plaintext
28 lines
884 B
Plaintext
"use strict";
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var isPrototype = require("../prototype/is");
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// In theory we could rely on Symbol.toStringTag directly,
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// still early native implementation (e.g. in FF) predated symbols
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var objectToString = Object.prototype.toString
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, objectTaggedString = objectToString.call(Promise.resolve());
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module.exports = function (value) {
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if (!value) return false;
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// Sanity check (reject objects which do not expose common Promise interface)
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try {
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if (typeof value.then !== "function") return false;
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if (typeof value["catch"] !== "function") return false;
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} catch (error) {
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return false;
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}
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// Ensure its native Promise object (has [[PromiseState]] slot)
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// Note: it's not 100% precise as string tag may be overriden
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// and other objects could be hacked to expose it
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if (objectToString.call(value) !== objectTaggedString) return false;
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return !isPrototype(value);
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};
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