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