emptyFunction.js

/**
 * Copyright 2013-2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule emptyFunction
 */

function makeEmptyFunction(arg) {
  return function() {
    return arg;
  };
}

/**
 * This function accepts and discards inputs; it has no side effects. This is
 * primarily useful idiomatically for overridable function endpoints which
 * always need to be callable, since JS lacks a null-call idiom ala Cocoa.
 */
function emptyFunction() {}

emptyFunction.thatReturns = makeEmptyFunction;
emptyFunction.thatReturnsFalse = makeEmptyFunction(false);
emptyFunction.thatReturnsTrue = makeEmptyFunction(true);
emptyFunction.thatReturnsNull = makeEmptyFunction(null);
emptyFunction.thatReturnsThis = function() { return this; };
emptyFunction.thatReturnsArgument = function(arg) { return arg; };

module.exports = emptyFunction;