lodash/lodash.merge/index.js

/**
 * lodash 3.2.1 (Custom Build) <https://lodash.com/>
 * Build: `lodash modern modularize exports="npm" -o ./`
 * Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */
var arrayCopy = require('lodash._arraycopy'),
    arrayEach = require('lodash._arrayeach'),
    createAssigner = require('lodash._createassigner'),
    isArguments = require('lodash.isarguments'),
    isArray = require('lodash.isarray'),
    isNative = require('lodash.isnative'),
    isPlainObject = require('lodash.isplainobject'),
    isTypedArray = require('lodash.istypedarray'),
    keys = require('lodash.keys'),
    keysIn = require('lodash.keysin'),
    toPlainObject = require('lodash.toplainobject');

/**
 * Checks if `value` is object-like.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is object-like, else `false`.
 */
function isObjectLike(value) {
  return !!value && typeof value == 'object';
}

/** Used for native method references. */
var arrayProto = Array.prototype;

/** Native method references. */
var getOwnPropertySymbols = isNative(getOwnPropertySymbols = Object.getOwnPropertySymbols) && getOwnPropertySymbols,
    push = arrayProto.push;

/**
 * Used as the [maximum length](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-number.max_safe_integer)
 * of an array-like value.
 */
var MAX_SAFE_INTEGER = Math.pow(2, 53) - 1;

/**
 * The base implementation of `_.merge` without support for argument juggling,
 * multiple sources, and `this` binding `customizer` functions.
 *
 * @private
 * @param {Object} object The destination object.
 * @param {Object} source The source object.
 * @param {Function} [customizer] The function to customize merging properties.
 * @param {Array} [stackA=[]] Tracks traversed source objects.
 * @param {Array} [stackB=[]] Associates values with source counterparts.
 * @returns {Object} Returns `object`.
 */
function baseMerge(object, source, customizer, stackA, stackB) {
  if (!isObject(object)) {
    return object;
  }
  var isSrcArr = isArrayLike(source) && (isArray(source) || isTypedArray(source));
  if (!isSrcArr) {
    var props = keys(source);
    push.apply(props, getSymbols(source));
  }
  arrayEach(props || source, function(srcValue, key) {
    if (props) {
      key = srcValue;
      srcValue = source[key];
    }
    if (isObjectLike(srcValue)) {
      stackA || (stackA = []);
      stackB || (stackB = []);
      baseMergeDeep(object, source, key, baseMerge, customizer, stackA, stackB);
    }
    else {
      var value = object[key],
          result = customizer ? customizer(value, srcValue, key, object, source) : undefined,
          isCommon = result === undefined;

      if (isCommon) {
        result = srcValue;
      }
      if ((isSrcArr || result !== undefined) &&
          (isCommon || (result === result ? (result !== value) : (value === value)))) {
        object[key] = result;
      }
    }
  });
  return object;
}

/**
 * A specialized version of `baseMerge` for arrays and objects which performs
 * deep merges and tracks traversed objects enabling objects with circular
 * references to be merged.
 *
 * @private
 * @param {Object} object The destination object.
 * @param {Object} source The source object.
 * @param {string} key The key of the value to merge.
 * @param {Function} mergeFunc The function to merge values.
 * @param {Function} [customizer] The function to customize merging properties.
 * @param {Array} [stackA=[]] Tracks traversed source objects.
 * @param {Array} [stackB=[]] Associates values with source counterparts.
 * @returns {boolean} Returns `true` if the objects are equivalent, else `false`.
 */
function baseMergeDeep(object, source, key, mergeFunc, customizer, stackA, stackB) {
  var length = stackA.length,
      srcValue = source[key];

  while (length--) {
    if (stackA[length] == srcValue) {
      object[key] = stackB[length];
      return;
    }
  }
  var value = object[key],
      result = customizer ? customizer(value, srcValue, key, object, source) : undefined,
      isCommon = result === undefined;

  if (isCommon) {
    result = srcValue;
    if (isArrayLike(srcValue) && (isArray(srcValue) || isTypedArray(srcValue))) {
      result = isArray(value)
        ? value
        : (isArrayLike(value) ? arrayCopy(value) : []);
    }
    else if (isPlainObject(srcValue) || isArguments(srcValue)) {
      result = isArguments(value)
        ? toPlainObject(value)
        : (isPlainObject(value) ? value : {});
    }
    else {
      isCommon = false;
    }
  }
  // Add the source value to the stack of traversed objects and associate
  // it with its merged value.
  stackA.push(srcValue);
  stackB.push(result);

  if (isCommon) {
    // Recursively merge objects and arrays (susceptible to call stack limits).
    object[key] = mergeFunc(result, srcValue, customizer, stackA, stackB);
  } else if (result === result ? (result !== value) : (value === value)) {
    object[key] = result;
  }
}

/**
 * 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];
  };
}

/**
 * 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');

/**
 * Creates an array of the own symbols of `object`.
 *
 * @private
 * @param {Object} object The object to query.
 * @returns {Array} Returns the array of symbols.
 */
var getSymbols = !getOwnPropertySymbols ? constant([]) : function(object) {
  return getOwnPropertySymbols(toObject(object));
};

/**
 * Checks if `value` is array-like.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
 */
function isArrayLike(value) {
  return value != null && isLength(getLength(value));
}

/**
 * Checks if `value` is a valid array-like length.
 *
 * **Note:** This function is based on [`ToLength`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength).
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
 */
function isLength(value) {
  return typeof value == 'number' && value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
}

/**
 * Converts `value` to an object if it is not one.
 *
 * @private
 * @param {*} value The value to process.
 * @returns {Object} Returns the object.
 */
function toObject(value) {
  return isObject(value) ? value : Object(value);
}

/**
 * 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(1);
 * // => false
 */
function isObject(value) {
  // Avoid a V8 JIT bug in Chrome 19-20.
  // See https://code.google.com/p/v8/issues/detail?id=2291 for more details.
  var type = typeof value;
  return type == 'function' || (!!value && type == 'object');
}

/**
 * Recursively merges own enumerable properties of the source object(s), that
 * don't resolve to `undefined` into the destination object. Subsequent sources
 * overwrite property assignments of previous sources. If `customizer` is
 * provided it is invoked to produce the merged values of the destination and
 * source properties. If `customizer` returns `undefined` merging is handled
 * by the method instead. The `customizer` is bound to `thisArg` and invoked
 * with five arguments: (objectValue, sourceValue, key, object, source).
 *
 * @static
 * @memberOf _
 * @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
 *
 * var users = {
 *   'data': [{ 'user': 'barney' }, { 'user': 'fred' }]
 * };
 *
 * var ages = {
 *   'data': [{ 'age': 36 }, { 'age': 40 }]
 * };
 *
 * _.merge(users, ages);
 * // => { 'data': [{ 'user': 'barney', 'age': 36 }, { 'user': 'fred', 'age': 40 }] }
 *
 * // using a customizer callback
 * var object = {
 *   'fruits': ['apple'],
 *   'vegetables': ['beet']
 * };
 *
 * var other = {
 *   'fruits': ['banana'],
 *   'vegetables': ['carrot']
 * };
 *
 * _.merge(object, other, function(a, b) {
 *   if (_.isArray(a)) {
 *     return a.concat(b);
 *   }
 * });
 * // => { 'fruits': ['apple', 'banana'], 'vegetables': ['beet', 'carrot'] }
 */
var merge = createAssigner(baseMerge);

/**
 * Creates a function that returns `value`.
 *
 * @static
 * @memberOf _
 * @category Utility
 * @param {*} value The value to return from the new function.
 * @returns {Function} Returns the new function.
 * @example
 *
 * var object = { 'user': 'fred' };
 * var getter = _.constant(object);
 *
 * getter() === object;
 * // => true
 */
function constant(value) {
  return function() {
    return value;
  };
}

module.exports = merge;