lodash/internal/isIterateeCall.js

import isIndex from './isIndex';
import isLength from './isLength';
import isObject from '../lang/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;
}

export default isIterateeCall;