'use strict'; var wellKnownSymbol = require('../internals/well-known-symbol'); var defineProperty = require('../internals/object-define-property').f; var METADATA = wellKnownSymbol('metadata'); var FunctionPrototype = Function.prototype; // Function.prototype[@@metadata] // https://github.com/tc39/proposal-decorator-metadata if (FunctionPrototype[METADATA] === undefined) { defineProperty(FunctionPrototype, METADATA, { value: null }); }