lodash/object/assign.js

define(['../internal/assignWith', '../internal/baseAssign', '../internal/createAssigner'], function(assignWith, baseAssign, createAssigner) {

  /**
   * Assigns own enumerable properties of source object(s) to the destination
   * object. Subsequent sources overwrite property assignments of previous sources.
   * If `customizer` is provided it is invoked to produce the assigned values.
   * The `customizer` is bound to `thisArg` and invoked with five arguments:
   * (objectValue, sourceValue, key, object, source).
   *
   * **Note:** This method mutates `object` and is based on
   * [`Object.assign`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.assign).
   *
   * @static
   * @memberOf _
   * @alias extend
   * @category Object
   * @param {Object} object The destination object.
   * @param {...Object} [sources] The source objects.
   * @param {Function} [customizer] The function to customize assigned values.
   * @param {*} [thisArg] The `this` binding of `customizer`.
   * @returns {Object} Returns `object`.
   * @example
   *
   * _.assign({ 'user': 'barney' }, { 'age': 40 }, { 'user': 'fred' });
   * // => { 'user': 'fred', 'age': 40 }
   *
   * // using a customizer callback
   * var defaults = _.partialRight(_.assign, function(value, other) {
   *   return _.isUndefined(value) ? other : value;
   * });
   *
   * defaults({ 'user': 'barney' }, { 'age': 36 }, { 'user': 'fred' });
   * // => { 'user': 'barney', 'age': 36 }
   */
  var assign = createAssigner(function(object, source, customizer) {
    return customizer
      ? assignWith(object, source, customizer)
      : baseAssign(object, source);
  });

  return assign;
});