@webcomponents/webcomponentsjs/src/platform/symbol.js

Web Components Polyfills

/**
@license
Copyright (c) 2018 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at
http://polymer.github.io/LICENSE.txt The complete set of authors may be found at
http://polymer.github.io/AUTHORS.txt The complete set of contributors may be
found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by Google as
part of the polymer project is also subject to an additional IP rights grant
found at http://polymer.github.io/PATENTS.txt
*/
// import polyfill for Symbol and Object.getOwnPropertySymbols
import 'get-own-property-symbols/build/get-own-property-symbols.max';
// Fix issue in toString patch when compiled into strict mode via closure
// https://github.com/es-shims/get-own-property-symbols/issues/16
const toString = Object.prototype.toString;
Object.prototype.toString = function () {
    if (this === undefined) {
        return '[object Undefined]';
    }
    else if (this === null) {
        return '[object Null]';
    }
    else {
        return toString.call(this);
    }
};
// overwrite Object.keys to filter out symbols
Object.keys = function (obj) {
    return Object.getOwnPropertyNames(obj).filter((name) => {
        const prop = Object.getOwnPropertyDescriptor(obj, name);
        return prop && prop.enumerable;
    });
};
// implement iterators for IE 11
if (!String.prototype[Symbol.iterator] || !String.prototype.codePointAt) {
    String.prototype[Symbol.iterator] = function* () {
        for (let i = 0; i < this.length; i++) {
            yield this[i];
        }
    };
}
if (!Set.prototype[Symbol.iterator]) {
    Set.prototype[Symbol.iterator] = function* () {
        const temp = [];
        this.forEach((value) => {
            temp.push(value);
        });
        for (let i = 0; i < temp.length; i++) {
            yield temp[i];
        }
    };
}
if (!Map.prototype[Symbol.iterator]) {
    Map.prototype[Symbol.iterator] = function* () {
        const entries = [];
        this.forEach((value, key) => {
            entries.push([key, value]);
        });
        for (let i = 0; i < entries.length; i++) {
            yield entries[i];
        }
    };
}
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