lodash/internal/isIterateeCall.js

define(['./isIndex', './isLength', '../lang/isObject'], function(isIndex, isLength, isObject) {

  /**
   * Checks if the provided 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') {
      var length = object.length,
          prereq = isLength(length) && isIndex(index, length);
    } else {
      prereq = type == 'string' && index in object;
    }
    if (prereq) {
      var other = object[index];
      return value === value ? value === other : other !== other;
    }
    return false;
  }

  return isIterateeCall;
});