es.function.has-instance.js 926 B

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  1. 'use strict';
  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');
  6. var HAS_INSTANCE = wellKnownSymbol('hasInstance');
  7. var FunctionPrototype = Function.prototype;
  8. // `Function.prototype[@@hasInstance]` method
  9. // https://tc39.es/ecma262/#sec-function.prototype-@@hasinstance
  10. if (!(HAS_INSTANCE in FunctionPrototype)) {
  11. definePropertyModule.f(FunctionPrototype, HAS_INSTANCE, { value: function (O) {
  12. if (typeof this != 'function' || !isObject(O)) return false;
  13. if (!isObject(this.prototype)) return O instanceof this;
  14. // for environment w/o native `@@hasInstance` logic enough `instanceof`, but add this:
  15. while (O = getPrototypeOf(O)) if (this.prototype === O) return true;
  16. return false;
  17. } });
  18. }