index.js
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var hasOwn = Object.prototype.hasOwnProperty;
var toStr = Object.prototype.toString;
var undefined;
var isArray = function isArray(arr) {
if (typeof Array.isArray === 'function') {
return Array.isArray(arr);
}
return toStr.call(arr) === '[object Array]';
};
var isPlainObject = function isPlainObject(obj) {
'use strict';
if (!obj || toStr.call(obj) !== '[object Object]') {
return false;
}
var has_own_constructor = hasOwn.call(obj, 'constructor');
var has_is_property_of_method = obj.constructor && obj.constructor.prototype && hasOwn.call(obj.constructor.prototype, 'isPrototypeOf');
// Not own constructor property must be Object
if (obj.constructor && !has_own_constructor && !has_is_property_of_method) {
return false;
}
// Own properties are enumerated firstly, so to speed up,
// if last one is own, then all properties are own.
var key;
for (key in obj) {}
return key === undefined || hasOwn.call(obj, key);
};
module.exports = function extend() {
'use strict';
var options, name, src, copy, copyIsArray, clone,
target = arguments[0],
i = 1,
length = arguments.length,
deep = false;
// Handle a deep copy situation
if (typeof target === 'boolean') {
deep = target;
target = arguments[1] || {};
// skip the boolean and the target
i = 2;
} else if ((typeof target !== 'object' && typeof target !== 'function') || target == null) {
target = {};
}
for (; i < length; ++i) {
options = arguments[i];
// Only deal with non-null/undefined values
if (options != null) {
// Extend the base object
for (name in options) {
src = target[name];
copy = options[name];
// Prevent never-ending loop
if (target === copy) {
continue;
}
// Recurse if we're merging plain objects or arrays
if (deep && copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
if (copyIsArray) {
copyIsArray = false;
clone = src && isArray(src) ? src : [];
} else {
clone = src && isPlainObject(src) ? src : {};
}
// Never move original objects, clone them
target[name] = extend(deep, clone, copy);
// Don't bring in undefined values
} else if (copy !== undefined) {
target[name] = copy;
}
}
}
}
// Return the modified object
return target;
};