michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "unstable"
michael@0: };
michael@0: 
michael@0: const { flatten } = require('./array');
michael@0: 
michael@0: /**
michael@0:  * Merges all the properties of all arguments into first argument. If two or
michael@0:  * more argument objects have own properties with the same name, the property
michael@0:  * is overridden, with precedence from right to left, implying, that properties
michael@0:  * of the object on the left are overridden by a same named property of the
michael@0:  * object on the right.
michael@0:  *
michael@0:  * Any argument given with "falsy" value - commonly `null` and `undefined` in
michael@0:  * case of objects - are skipped.
michael@0:  *
michael@0:  * @examples
michael@0:  *    var a = { bar: 0, a: 'a' }
michael@0:  *    var b = merge(a, { foo: 'foo', bar: 1 }, { foo: 'bar', name: 'b' });
michael@0:  *    b === a   // true
michael@0:  *    b.a       // 'a'
michael@0:  *    b.foo     // 'bar'
michael@0:  *    b.bar     // 1
michael@0:  *    b.name    // 'b'
michael@0:  */
michael@0: function merge(source) {
michael@0:   let descriptor = {};
michael@0: 
michael@0:   // `Boolean` converts the first parameter to a boolean value. Any object is
michael@0:   // converted to `true` where `null` and `undefined` becames `false`. Therefore
michael@0:   // the `filter` method will keep only objects that are defined and not null.
michael@0:   Array.slice(arguments, 1).filter(Boolean).forEach(function onEach(properties) {
michael@0:     Object.getOwnPropertyNames(properties).forEach(function(name) {
michael@0:       descriptor[name] = Object.getOwnPropertyDescriptor(properties, name);
michael@0:     });
michael@0:   });
michael@0:   return Object.defineProperties(source, descriptor);
michael@0: }
michael@0: exports.merge = merge;
michael@0: 
michael@0: /**
michael@0:  * Returns an object that inherits from the first argument and contains all the
michael@0:  * properties from all following arguments.
michael@0:  * `extend(source1, source2, source3)` is equivalent of
michael@0:  * `merge(Object.create(source1), source2, source3)`.
michael@0:  */
michael@0: function extend(source) {
michael@0:   let rest = Array.slice(arguments, 1);
michael@0:   rest.unshift(Object.create(source));
michael@0:   return merge.apply(null, rest);
michael@0: }
michael@0: exports.extend = extend;
michael@0: 
michael@0: function has(obj, key) obj.hasOwnProperty(key);
michael@0: exports.has = has;
michael@0: 
michael@0: function each(obj, fn) {
michael@0:   for (let key in obj) has(obj, key) && fn(obj[key], key, obj);
michael@0: }
michael@0: exports.each = each;
michael@0: 
michael@0: /**
michael@0:  * Like `merge`, except no property descriptors are manipulated, for use
michael@0:  * with platform objects. Identical to underscore's `extend`. Useful for
michael@0:  * merging XPCOM objects
michael@0:  */
michael@0: function safeMerge(source) {
michael@0:   Array.slice(arguments, 1).forEach(function onEach (obj) {
michael@0:     for (let prop in obj) source[prop] = obj[prop];
michael@0:   });
michael@0:   return source;
michael@0: }
michael@0: exports.safeMerge = safeMerge;
michael@0: 
michael@0: /*
michael@0:  * Returns a copy of the object without blacklisted properties
michael@0:  */
michael@0: function omit(source, ...values) {
michael@0:   let copy = {};
michael@0:   let keys = flatten(values);
michael@0:   for (let prop in source)
michael@0:     if (!~keys.indexOf(prop)) 
michael@0:       copy[prop] = source[prop];
michael@0:   return copy;
michael@0: }
michael@0: exports.omit = omit;