2 var isObject = require('../internals/is-object');
3 var definePropertyModule = require('../internals/object-define-property');
4 var getPrototypeOf = require('../internals/object-get-prototype-of');
5 var wellKnownSymbol = require('../internals/well-known-symbol');
7 var HAS_INSTANCE = wellKnownSymbol('hasInstance');
8 var FunctionPrototype = Function.prototype;
10 // `Function.prototype[@@hasInstance]` method
11 // https://tc39.github.io/ecma262/#sec-function.prototype-@@hasinstance
12 if (!(HAS_INSTANCE in FunctionPrototype)) {
13 definePropertyModule.f(FunctionPrototype, HAS_INSTANCE, { value: function (O) {
14 if (typeof this != 'function' || !isObject(O)) return false;
15 if (!isObject(this.prototype)) return O instanceof this;
16 // for environment w/o native `@@hasInstance` logic enough `instanceof`, but add this:
17 while (O = getPrototypeOf(O)) if (this.prototype === O) return true;