baseClone.js

var arrayCopy = require('./arrayCopy'),
    arrayEach = require('./arrayEach'),
    baseAssign = require('./baseAssign'),
    baseForOwn = require('./baseForOwn'),
    initCloneArray = require('./initCloneArray'),
    initCloneByTag = require('./initCloneByTag'),
    initCloneObject = require('./initCloneObject'),
    isArray = require('../lang/isArray'),
    isObject = require('../lang/isObject');

/** `Object#toString` result references. */
var argsTag = '[object Arguments]',
    arrayTag = '[object Array]',
    boolTag = '[object Boolean]',
    dateTag = '[object Date]',
    errorTag = '[object Error]',
    funcTag = '[object Function]',
    mapTag = '[object Map]',
    numberTag = '[object Number]',
    objectTag = '[object Object]',
    regexpTag = '[object RegExp]',
    setTag = '[object Set]',
    stringTag = '[object String]',
    weakMapTag = '[object WeakMap]';

var arrayBufferTag = '[object ArrayBuffer]',
    float32Tag = '[object Float32Array]',
    float64Tag = '[object Float64Array]',
    int8Tag = '[object Int8Array]',
    int16Tag = '[object Int16Array]',
    int32Tag = '[object Int32Array]',
    uint8Tag = '[object Uint8Array]',
    uint8ClampedTag = '[object Uint8ClampedArray]',
    uint16Tag = '[object Uint16Array]',
    uint32Tag = '[object Uint32Array]';

/** Used to identify `toStringTag` values supported by `_.clone`. */
var cloneableTags = {};
cloneableTags[argsTag] = cloneableTags[arrayTag] =
cloneableTags[arrayBufferTag] = cloneableTags[boolTag] =
cloneableTags[dateTag] = cloneableTags[float32Tag] =
cloneableTags[float64Tag] = cloneableTags[int8Tag] =
cloneableTags[int16Tag] = cloneableTags[int32Tag] =
cloneableTags[numberTag] = cloneableTags[objectTag] =
cloneableTags[regexpTag] = cloneableTags[stringTag] =
cloneableTags[uint8Tag] = cloneableTags[uint8ClampedTag] =
cloneableTags[uint16Tag] = cloneableTags[uint32Tag] = true;
cloneableTags[errorTag] = cloneableTags[funcTag] =
cloneableTags[mapTag] = cloneableTags[setTag] =
cloneableTags[weakMapTag] = false;

/** Used for native method references. */
var objectProto = Object.prototype;

/**
 * Used to resolve the [`toStringTag`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.prototype.tostring)
 * of values.
 */
var objToString = objectProto.toString;

/**
 * The base implementation of `_.clone` without support for argument juggling
 * and `this` binding `customizer` functions.
 *
 * @private
 * @param {*} value The value to clone.
 * @param {boolean} [isDeep] Specify a deep clone.
 * @param {Function} [customizer] The function to customize cloning values.
 * @param {string} [key] The key of `value`.
 * @param {Object} [object] The object `value` belongs to.
 * @param {Array} [stackA=[]] Tracks traversed source objects.
 * @param {Array} [stackB=[]] Associates clones with source counterparts.
 * @returns {*} Returns the cloned value.
 */
function baseClone(value, isDeep, customizer, key, object, stackA, stackB) {
  var result;
  if (customizer) {
    result = object ? customizer(value, key, object) : customizer(value);
  }
  if (result !== undefined) {
    return result;
  }
  if (!isObject(value)) {
    return value;
  }
  var isArr = isArray(value);
  if (isArr) {
    result = initCloneArray(value);
    if (!isDeep) {
      return arrayCopy(value, result);
    }
  } else {
    var tag = objToString.call(value),
        isFunc = tag == funcTag;

    if (tag == objectTag || tag == argsTag || (isFunc && !object)) {
      result = initCloneObject(isFunc ? {} : value);
      if (!isDeep) {
        return baseAssign(result, value);
      }
    } else {
      return cloneableTags[tag]
        ? initCloneByTag(value, tag, isDeep)
        : (object ? value : {});
    }
  }
  // Check for circular references and return corresponding clone.
  stackA || (stackA = []);
  stackB || (stackB = []);

  var length = stackA.length;
  while (length--) {
    if (stackA[length] == value) {
      return stackB[length];
    }
  }
  // Add the source value to the stack of traversed objects and associate it with its clone.
  stackA.push(value);
  stackB.push(result);

  // Recursively populate clone (susceptible to call stack limits).
  (isArr ? arrayEach : baseForOwn)(value, function(subValue, key) {
    result[key] = baseClone(subValue, isDeep, customizer, key, value, stackA, stackB);
  });
  return result;
}

module.exports = baseClone;