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1'use strict';
2
3var hasOwn = Object.prototype.hasOwnProperty;
4var toStr = Object.prototype.toString;
5var defineProperty = Object.defineProperty;
6var gOPD = Object.getOwnPropertyDescriptor;
7
8var isArray = function isArray(arr) {
9	if (typeof Array.isArray === 'function') {
10		return Array.isArray(arr);
11	}
12
13	return toStr.call(arr) === '[object Array]';
14};
15
16var isPlainObject = function isPlainObject(obj) {
17	if (!obj || toStr.call(obj) !== '[object Object]') {
18		return false;
19	}
20
21	var hasOwnConstructor = hasOwn.call(obj, 'constructor');
22	var hasIsPrototypeOf = obj.constructor && obj.constructor.prototype && hasOwn.call(obj.constructor.prototype, 'isPrototypeOf');
23	// Not own constructor property must be Object
24	if (obj.constructor && !hasOwnConstructor && !hasIsPrototypeOf) {
25		return false;
26	}
27
28	// Own properties are enumerated firstly, so to speed up,
29	// if last one is own, then all properties are own.
30	var key;
31	for (key in obj) { /**/ }
32
33	return typeof key === 'undefined' || hasOwn.call(obj, key);
34};
35
36// If name is '__proto__', and Object.defineProperty is available, define __proto__ as an own property on target
37var setProperty = function setProperty(target, options) {
38	if (defineProperty && options.name === '__proto__') {
39		defineProperty(target, options.name, {
40			enumerable: true,
41			configurable: true,
42			value: options.newValue,
43			writable: true
44		});
45	} else {
46		target[options.name] = options.newValue;
47	}
48};
49
50// Return undefined instead of __proto__ if '__proto__' is not an own property
51var getProperty = function getProperty(obj, name) {
52	if (name === '__proto__') {
53		if (!hasOwn.call(obj, name)) {
54			return void 0;
55		} else if (gOPD) {
56			// In early versions of node, obj['__proto__'] is buggy when obj has
57			// __proto__ as an own property. Object.getOwnPropertyDescriptor() works.
58			return gOPD(obj, name).value;
59		}
60	}
61
62	return obj[name];
63};
64
65module.exports = function extend() {
66	var options, name, src, copy, copyIsArray, clone;
67	var target = arguments[0];
68	var i = 1;
69	var length = arguments.length;
70	var deep = false;
71
72	// Handle a deep copy situation
73	if (typeof target === 'boolean') {
74		deep = target;
75		target = arguments[1] || {};
76		// skip the boolean and the target
77		i = 2;
78	}
79	if (target == null || (typeof target !== 'object' && typeof target !== 'function')) {
80		target = {};
81	}
82
83	for (; i < length; ++i) {
84		options = arguments[i];
85		// Only deal with non-null/undefined values
86		if (options != null) {
87			// Extend the base object
88			for (name in options) {
89				src = getProperty(target, name);
90				copy = getProperty(options, name);
91
92				// Prevent never-ending loop
93				if (target !== copy) {
94					// Recurse if we're merging plain objects or arrays
95					if (deep && copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
96						if (copyIsArray) {
97							copyIsArray = false;
98							clone = src && isArray(src) ? src : [];
99						} else {
100							clone = src && isPlainObject(src) ? src : {};
101						}
102
103						// Never move original objects, clone them
104						setProperty(target, { name: name, newValue: extend(deep, clone, copy) });
105
106					// Don't bring in undefined values
107					} else if (typeof copy !== 'undefined') {
108						setProperty(target, { name: name, newValue: copy });
109					}
110				}
111			}
112		}
113	}
114
115	// Return the modified object
116	return target;
117};
118