var assignWith = require('../internal/assignWith'),
    baseAssign = require('../internal/baseAssign'),
    createAssigner = require('../internal/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);
});

module.exports = assign;
