20 lines
933 B
JavaScript
20 lines
933 B
JavaScript
'use strict';
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var isObject = require('../internals/is-object');
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var definePropertyModule = require('../internals/object-define-property');
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var getPrototypeOf = require('../internals/object-get-prototype-of');
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var wellKnownSymbol = require('../internals/well-known-symbol');
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var HAS_INSTANCE = wellKnownSymbol('hasInstance');
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var FunctionPrototype = Function.prototype;
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// `Function.prototype[@@hasInstance]` method
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// https://tc39.github.io/ecma262/#sec-function.prototype-@@hasinstance
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if (!(HAS_INSTANCE in FunctionPrototype)) {
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definePropertyModule.f(FunctionPrototype, HAS_INSTANCE, { value: function (O) {
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if (typeof this != 'function' || !isObject(O)) return false;
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if (!isObject(this.prototype)) return O instanceof this;
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// for environment w/o native `@@hasInstance` logic enough `instanceof`, but add this:
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while (O = getPrototypeOf(O)) if (this.prototype === O) return true;
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return false;
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} });
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}
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