lodash/lodash._baseflatten/index.js

/**
 * lodash 3.0.0 (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 1.7.0 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */
var isArguments = require('lodash.isarguments'),
    isArray = require('lodash.isarray');

/**
 * 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') || false;
}

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

/**
 * The base implementation of `_.flatten` with added support for restricting
 * flattening and specifying the start index.
 *
 * @private
 * @param {Array} array The array to flatten.
 * @param {boolean} [isDeep] Specify a deep flatten.
 * @param {boolean} [isStrict] Restrict flattening to arrays and `arguments` objects.
 * @param {number} [fromIndex=0] The index to start from.
 * @returns {Array} Returns the new flattened array.
 */
function baseFlatten(array, isDeep, isStrict, fromIndex) {
  var index = (fromIndex || 0) - 1,
      length = array.length,
      resIndex = -1,
      result = [];

  while (++index < length) {
    var value = array[index];

    if (isObjectLike(value) && isLength(value.length) && (isArray(value) || isArguments(value))) {
      if (isDeep) {
        // Recursively flatten arrays (susceptible to call stack limits).
        value = baseFlatten(value, isDeep, isStrict);
      }
      var valIndex = -1,
          valLength = value.length;

      result.length += valLength;
      while (++valIndex < valLength) {
        result[++resIndex] = value[valIndex];
      }
    } else if (!isStrict) {
      result[++resIndex] = value;
    }
  }
  return result;
}

/**
 * Checks if `value` is a valid array-like length.
 *
 * **Note:** This function is based on ES `ToLength`. See the
 * [ES spec](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength)
 * for more details.
 *
 * @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;
}

module.exports = baseFlatten;