internal/baseClone.js

import Stack from './Stack';
import arrayEach from './arrayEach';
import assignValue from './assignValue';
import baseAssign from './baseAssign';
import baseForOwn from './baseForOwn';
import copyArray from './copyArray';
import copySymbols from './copySymbols';
import getTag from './getTag';
import initCloneArray from './initCloneArray';
import initCloneByTag from './initCloneByTag';
import initCloneObject from './initCloneObject';
import isArray from '../isArray';
import isHostObject from './isHostObject';
import isObject from '../isObject';

/** `Object#toString` result references. */
var argsTag = '[object Arguments]',
    arrayTag = '[object Array]',
    boolTag = '[object Boolean]',
    dateTag = '[object Date]',
    errorTag = '[object Error]',
    funcTag = '[object Function]',
    genTag = '[object GeneratorFunction]',
    mapTag = '[object Map]',
    numberTag = '[object Number]',
    objectTag = '[object Object]',
    regexpTag = '[object RegExp]',
    setTag = '[object Set]',
    stringTag = '[object String]',
    symbolTag = '[object Symbol]',
    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[mapTag] = cloneableTags[numberTag] =
cloneableTags[objectTag] = cloneableTags[regexpTag] =
cloneableTags[setTag] = cloneableTags[stringTag] =
cloneableTags[symbolTag] = cloneableTags[uint8Tag] =
cloneableTags[uint8ClampedTag] = cloneableTags[uint16Tag] =
cloneableTags[uint32Tag] = true;
cloneableTags[errorTag] = cloneableTags[funcTag] =
cloneableTags[weakMapTag] = false;

/**
 * The base implementation of `_.clone` and `_.cloneDeep` which tracks
 * traversed objects.
 *
 * @private
 * @param {*} value The value to clone.
 * @param {boolean} [isDeep] Specify a deep clone.
 * @param {Function} [customizer] The function to customize cloning.
 * @param {string} [key] The key of `value`.
 * @param {Object} [object] The parent object of `value`.
 * @param {Object} [stack] Tracks traversed objects and their clone counterparts.
 * @returns {*} Returns the cloned value.
 */
function baseClone(value, isDeep, customizer, key, object, stack) {
  var result;
  if (customizer) {
    result = object ? customizer(value, key, object, stack) : customizer(value);
  }
  if (result !== undefined) {
    return result;
  }
  if (!isObject(value)) {
    return value;
  }
  var isArr = isArray(value);
  if (isArr) {
    result = initCloneArray(value);
    if (!isDeep) {
      return copyArray(value, result);
    }
  } else {
    var tag = getTag(value),
        isFunc = tag == funcTag || tag == genTag;

    if (tag == objectTag || tag == argsTag || (isFunc && !object)) {
      if (isHostObject(value)) {
        return object ? value : {};
      }
      result = initCloneObject(isFunc ? {} : value);
      if (!isDeep) {
        return copySymbols(value, baseAssign(result, value));
      }
    } else {
      return cloneableTags[tag]
        ? initCloneByTag(value, tag, isDeep)
        : (object ? value : {});
    }
  }
  // Check for circular references and return its corresponding clone.
  stack || (stack = new Stack);
  var stacked = stack.get(value);
  if (stacked) {
    return stacked;
  }
  stack.set(value, result);

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

export default baseClone;