lodash/utility/callback.js

define(['../internal/baseCallback', '../internal/isIterateeCall', '../internal/isObjectLike', './matches'], function(baseCallback, isIterateeCall, isObjectLike, matches) {

  /**
   * Creates a function that invokes `func` with the `this` binding of `thisArg`
   * and arguments of the created function. If `func` is a property name the
   * created callback returns the property value for a given element. If `func`
   * is an object the created callback returns `true` for elements that contain
   * the equivalent object properties, otherwise it returns `false`.
   *
   * @static
   * @memberOf _
   * @alias iteratee
   * @category Utility
   * @param {*} [func=_.identity] The value to convert to a callback.
   * @param {*} [thisArg] The `this` binding of `func`.
   * @param- {Object} [guard] Enables use as a callback for functions like `_.map`.
   * @returns {Function} Returns the callback.
   * @example
   *
   * var users = [
   *   { 'user': 'barney', 'age': 36 },
   *   { 'user': 'fred',   'age': 40 }
   * ];
   *
   * // wrap to create custom callback shorthands
   * _.callback = _.wrap(_.callback, function(callback, func, thisArg) {
   *   var match = /^(.+?)__([gl]t)(.+)$/.exec(func);
   *   if (!match) {
   *     return callback(func, thisArg);
   *   }
   *   return function(object) {
   *     return match[2] == 'gt' ? object[match[1]] > match[3] : object[match[1]] < match[3];
   *   };
   * });
   *
   * _.filter(users, 'age__gt36');
   * // => [{ 'user': 'fred', 'age': 40 }]
   */
  function callback(func, thisArg, guard) {
    if (guard && isIterateeCall(func, thisArg, guard)) {
      thisArg = null;
    }
    return isObjectLike(func)
      ? matches(func)
      : baseCallback(func, thisArg);
  }

  return callback;
});