/**
   * lodash 4.0.4 (Custom Build) <https://lodash.com/>
   * Build: `lodash modularize exports="npm" -o ./`
   * Copyright 2012-2016 The Dojo Foundation <http://dojofoundation.org/>
   * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
   * Copyright 2009-2016 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
   * Available under MIT license <https://lodash.com/license>
   */
  var keys = require('lodash.keys'),
      rest = require('lodash.rest');
  
  /** Used as references for various `Number` constants. */
  var MAX_SAFE_INTEGER = 9007199254740991;
  
  /** `Object#toString` result references. */
  var funcTag = '[object Function]',
      genTag = '[object GeneratorFunction]';
  
  /** Used to detect unsigned integer values. */
  var reIsUint = /^(?:0|[1-9]\d*)$/;
  
  /**
   * Checks if `value` is a valid array-like index.
   *
   * @private
   * @param {*} value The value to check.
   * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
   * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
   */
  function isIndex(value, length) {
    value = (typeof value == 'number' || reIsUint.test(value)) ? +value : -1;
    length = length == null ? MAX_SAFE_INTEGER : length;
    return value > -1 && value % 1 == 0 && value < length;
  }
  
  /** Used for built-in method references. */
  var objectProto = Object.prototype;
  
  /** Used to check objects for own properties. */
  var hasOwnProperty = objectProto.hasOwnProperty;
  
  /**
   * Used to resolve the [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
   * of values.
   */
  var objectToString = objectProto.toString;
  
  /**
   * Assigns `value` to `key` of `object` if the existing value is not equivalent
   * using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
   * for equality comparisons.
   *
   * @private
   * @param {Object} object The object to modify.
   * @param {string} key The key of the property to assign.
   * @param {*} value The value to assign.
   */
  function assignValue(object, key, value) {
    var objValue = object[key];
    if (!(hasOwnProperty.call(object, key) && eq(objValue, value)) ||
        (value === undefined && !(key in object))) {
      object[key] = value;
    }
  }
  
  /**
   * The base implementation of `_.property` without support for deep paths.
   *
   * @private
   * @param {string} key The key of the property to get.
   * @returns {Function} Returns the new function.
   */
  function baseProperty(key) {
    return function(object) {
      return object == null ? undefined : object[key];
    };
  }
  
  /**
   * Copies properties of `source` to `object`.
   *
   * @private
   * @param {Object} source The object to copy properties from.
   * @param {Array} props The property names to copy.
   * @param {Object} [object={}] The object to copy properties to.
   * @returns {Object} Returns `object`.
   */
  function copyObject(source, props, object) {
    return copyObjectWith(source, props, object);
  }
  
  /**
   * This function is like `copyObject` except that it accepts a function to
   * customize copied values.
   *
   * @private
   * @param {Object} source The object to copy properties from.
   * @param {Array} props The property names to copy.
   * @param {Object} [object={}] The object to copy properties to.
   * @param {Function} [customizer] The function to customize copied values.
   * @returns {Object} Returns `object`.
   */
  function copyObjectWith(source, props, object, customizer) {
    object || (object = {});
  
    var index = -1,
        length = props.length;
  
    while (++index < length) {
      var key = props[index];
  
      var newValue = customizer
        ? customizer(object[key], source[key], key, object, source)
        : source[key];
  
      assignValue(object, key, newValue);
    }
    return object;
  }
  
  /**
   * Creates a function like `_.assign`.
   *
   * @private
   * @param {Function} assigner The function to assign values.
   * @returns {Function} Returns the new assigner function.
   */
  function createAssigner(assigner) {
    return rest(function(object, sources) {
      var index = -1,
          length = sources.length,
          customizer = length > 1 ? sources[length - 1] : undefined,
          guard = length > 2 ? sources[2] : undefined;
  
      customizer = typeof customizer == 'function'
        ? (length--, customizer)
        : undefined;
  
      if (guard && isIterateeCall(sources[0], sources[1], guard)) {
        customizer = length < 3 ? undefined : customizer;
        length = 1;
      }
      object = Object(object);
      while (++index < length) {
        var source = sources[index];
        if (source) {
          assigner(object, source, index, customizer);
        }
      }
      return object;
    });
  }
  
  /**
   * Gets the "length" property value of `object`.
   *
   * **Note:** This function is used to avoid a [JIT bug](https://bugs.webkit.org/show_bug.cgi?id=142792)
   * that affects Safari on at least iOS 8.1-8.3 ARM64.
   *
   * @private
   * @param {Object} object The object to query.
   * @returns {*} Returns the "length" value.
   */
  var getLength = baseProperty('length');
  
  /**
   * Checks if the given arguments are from an iteratee call.
   *
   * @private
   * @param {*} value The potential iteratee value argument.
   * @param {*} index The potential iteratee index or key argument.
   * @param {*} object The potential iteratee object argument.
   * @returns {boolean} Returns `true` if the arguments are from an iteratee call, else `false`.
   */
  function isIterateeCall(value, index, object) {
    if (!isObject(object)) {
      return false;
    }
    var type = typeof index;
    if (type == 'number'
        ? (isArrayLike(object) && isIndex(index, object.length))
        : (type == 'string' && index in object)) {
      return eq(object[index], value);
    }
    return false;
  }
  
  /**
   * Performs a [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
   * comparison between two values to determine if they are equivalent.
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to compare.
   * @param {*} other The other value to compare.
   * @returns {boolean} Returns `true` if the values are equivalent, else `false`.
   * @example
   *
   * var object = { 'user': 'fred' };
   * var other = { 'user': 'fred' };
   *
   * _.eq(object, object);
   * // => true
   *
   * _.eq(object, other);
   * // => false
   *
   * _.eq('a', 'a');
   * // => true
   *
   * _.eq('a', Object('a'));
   * // => false
   *
   * _.eq(NaN, NaN);
   * // => true
   */
  function eq(value, other) {
    return value === other || (value !== value && other !== other);
  }
  
  /**
   * Checks if `value` is array-like. A value is considered array-like if it's
   * not a function and has a `value.length` that's an integer greater than or
   * equal to `0` and less than or equal to `Number.MAX_SAFE_INTEGER`.
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to check.
   * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
   * @example
   *
   * _.isArrayLike([1, 2, 3]);
   * // => true
   *
   * _.isArrayLike(document.body.children);
   * // => true
   *
   * _.isArrayLike('abc');
   * // => true
   *
   * _.isArrayLike(_.noop);
   * // => false
   */
  function isArrayLike(value) {
    return value != null &&
      !(typeof value == 'function' && isFunction(value)) && isLength(getLength(value));
  }
  
  /**
   * Checks if `value` is classified as a `Function` object.
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to check.
   * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
   * @example
   *
   * _.isFunction(_);
   * // => true
   *
   * _.isFunction(/abc/);
   * // => false
   */
  function isFunction(value) {
    // The use of `Object#toString` avoids issues with the `typeof` operator
    // in Safari 8 which returns 'object' for typed array constructors, and
    // PhantomJS 1.9 which returns 'function' for `NodeList` instances.
    var tag = isObject(value) ? objectToString.call(value) : '';
    return tag == funcTag || tag == genTag;
  }
  
  /**
   * Checks if `value` is a valid array-like length.
   *
   * **Note:** This function is loosely based on [`ToLength`](http://ecma-international.org/ecma-262/6.0/#sec-tolength).
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to check.
   * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
   * @example
   *
   * _.isLength(3);
   * // => true
   *
   * _.isLength(Number.MIN_VALUE);
   * // => false
   *
   * _.isLength(Infinity);
   * // => false
   *
   * _.isLength('3');
   * // => false
   */
  function isLength(value) {
    return typeof value == 'number' &&
      value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
  }
  
  /**
   * Checks if `value` is the [language type](https://es5.github.io/#x8) of `Object`.
   * (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
   *
   * @static
   * @memberOf _
   * @category Lang
   * @param {*} value The value to check.
   * @returns {boolean} Returns `true` if `value` is an object, else `false`.
   * @example
   *
   * _.isObject({});
   * // => true
   *
   * _.isObject([1, 2, 3]);
   * // => true
   *
   * _.isObject(_.noop);
   * // => true
   *
   * _.isObject(null);
   * // => false
   */
  function isObject(value) {
    var type = typeof value;
    return !!value && (type == 'object' || type == 'function');
  }
  
  /**
   * Assigns own enumerable properties of source objects to the destination
   * object. Source objects are applied from left to right. Subsequent sources
   * overwrite property assignments of previous sources.
   *
   * **Note:** This method mutates `object` and is loosely based on
   * [`Object.assign`](https://mdn.io/Object/assign).
   *
   * @static
   * @memberOf _
   * @category Object
   * @param {Object} object The destination object.
   * @param {...Object} [sources] The source objects.
   * @returns {Object} Returns `object`.
   * @example
   *
   * function Foo() {
   *   this.c = 3;
   * }
   *
   * function Bar() {
   *   this.e = 5;
   * }
   *
   * Foo.prototype.d = 4;
   * Bar.prototype.f = 6;
   *
   * _.assign({ 'a': 1 }, new Foo, new Bar);
   * // => { 'a': 1, 'c': 3, 'e': 5 }
   */
  var assign = createAssigner(function(object, source) {
    copyObject(source, keys(source), object);
  });
  
  module.exports = assign;