JavaScript Passing parameters to a callback function

Question

I m trying to pass some parameter to a function used as callback  how can I do that   function tryMe  param1  param2        alert  param1     and     param2      function callbackTester  callback  param1  param2        callback  param1  param2      callbackTester  tryMe   hello    goodbye

User · Accepted Answer

If you want something slightly more general, you can use the arguments variable like so:

function tryMe (param1, param2) {
    alert(param1 + " and " + param2);
}

function callbackTester (callback) {
    callback (arguments[1], arguments[2]);
}

callbackTester (tryMe, "hello", "goodbye");

But otherwise, your example works fine (arguments[0] can be used in place of callback in the tester)

User · Answer

Wrap the  child  function s  being passed as with arguments within function wrappers to prevent them being evaluated when the  parent  function is called   function outcome        return false     function process callbackSuccess  callbackFailure       if   outcome             callbackSuccess        else         callbackFailure       process function   alert  OKAY     function   alert  OOPS

User · Answer

function tryMe param1  param2      console log param1     and     param2      function tryMe2 param1      console log param1      function callbackTester callback     params      callback    params        callbackTester tryMe   hello    goodbye     callbackTester tryMe2   hello      read more about the spread syntax

User · Answer

When you have a callback that will be called by something other than your code with a specific number of params and you want to pass in additional params you can pass a wrapper function as the callback and inside the wrapper pass the additional param s     function login accessedViaPopup          pass FB login a call back function wrapper that will accept the       response param and then call my  real  callback with the additional param     FB login function response           fb login callback response accessedViaPopup                handles respone from fb login call function fb login callback response  accessedViaPopup          do stuff

User · Answer

A new version for the scenario where the callback will be called by some other function  not your own code  and you want to add additional parameters   For example  let s pretend that you have a lot of nested calls with success and error callbacks  I will use angular promises for this example but any javascript code with callbacks would be the same for the purpose   someObject doSomething param1  function result1      console log  Got result from doSomething      result1     result doSomethingElse param2  function result2        console log  Got result from doSomethingElse      result2        function error2        console log  Got error from doSomethingElse      error2            function error1      console log  Got error from doSomething      error1         Now you may want to unclutter your code by defining a function to log errors  keeping the origin of the error for debugging purposes  This is how you would proceed to refactor your code   someObject doSomething param1  function  result1      console log  Got result from doSomething      result1     result doSomethingElse param2  function  result2        console log  Got result from doSomethingElse      result2        handleError bind null   doSomethingElse        handleError bind null   doSomething            Log errors  capturing the error of a callback and prepending an id     var handleError   function  id  error      var id   id          console log  Got error from     id          error        The calling function will still add the error parameter after your callback function parameters

User · Answer

Suppose function not taking any parameter means just add the GetAlterConfirmation function result       GetAlterConfirmation  test   messageText  function result                            alert result             Function into document load or any other click event    function GetAlterConfirmation titleText  messageText   callback            bootbox confirm                       title  titleText                      message  messageText                      buttons                            cancel                                label    lt i class  fa fa-times  gt  lt  i gt  Cancel                                                     confirm                                label    lt i class  fa fa-check  gt  lt  i gt  Confirm                                                                       callback  function  result                            return  callback result

User · Answer

If you are not sure how many parameters are you going to be passed into callback functions  use apply function   function tryMe  param1  param2      alert  param1     and     param2      function callbackTester callback params       callback apply this params      callbackTester tryMe   hello   goodbye

User · Answer

Code from a question with any number of parameters and a callback context   function SomeFunction name        this name   name    function tryMe param1  param2        console log this name           param1     and     param2     function tryMeMore param1  param2  param3        console log this name          param1     and     param2     and even     param3     function callbackTester callback  callbackContext        callback apply callbackContext  Array prototype splice call arguments  2      callbackTester tryMe  new SomeFunction  context1     hello    goodbye    callbackTester tryMeMore  new SomeFunction  context2     hello    goodbye    hasta la vista        context1  hello and goodbye    context2  hello and goodbye and even hasta la vista

User · Answer

Your question is unclear   If you re asking how you can do this in a simpler way  you should take a look at the ECMAScript 5th edition method  bind    which is a member of Function prototype   Using it  you can do something like this   function tryMe  param1  param2        alert  param1     and     param2      function callbackTester  callback        callback       callbackTester tryMe bind null   hello    goodbye       You can also use the following code  which adds the method if it isn t available in the current browser      From Prototype js if   Function prototype bind       check if native implementation available   Function prototype bind   function         var fn   this  args   Array prototype slice call arguments           object   args shift         return function           return fn apply object           args concat Array prototype slice call arguments                       Example  bind   - PrototypeJS Documentation

User · Answer

I was looking for the same thing and end up with the solution and here it s a simple example if anybody wants to go through this   var FA   function data      console log  IN A   data     FC data  LastName       var FC   function data d2      console log  IN C   data d2     var FB   function data      console log  IN B   data       FA data     FB  FirstName     Also posted on the other question here

User · Answer

Use curried function as in this simple example    x000D   x000D  const BTN   document querySelector  button   x000D  const RES   document querySelector  p   x000D   x000D  const changeText   newText   gt       gt    x000D    RES textContent   newText x000D    x000D   x000D  BTN addEventListener  click   changeText  Clicked     x000D   lt button gt ClickMe lt  button gt  x000D   lt p gt Not clicked lt p gt  x000D   x000D   x000D

User · Answer

This would also work      callback function function tryMe  param1  param2         alert  param1     and     param2           callback executer  function callbackTester  callback         callback            test function callbackTester  function         tryMe  hello    goodbye            Another Scenario       callback function function tryMe  param1  param2  param3         alert  param1     and     param2         param3           callback executer  function callbackTester  callback       this is the more obivous scenario as we use callback function   only when we have some missing value   get this data from ajax or compute var extraParam    this data was missing       call the callback when we have the data     callback extraParam           test function callbackTester  function k        tryMe  hello    goodbye   k

User · Answer

Let me give you a very plain Node js style example of using a callback          Function expects these arguments      2 numbers and a callback function err  result      var myTest   function arg1  arg2  callback      if  typeof arg1      number         return callback  Arg 1 is not a number    null      Args  1 Error  2 No result       if  typeof arg2      number         return callback  Arg 2 is not a number    null      Args  1 Error  2 No result       if  arg1     arg2           Do somethign complex here       callback null   Actions ended  arg1 was equal to arg2       Args  1 No error  2 Result     else if  arg1  gt  arg2           Do somethign complex here       callback null   Actions ended  arg1 was  gt  from arg2       Args  1 No error  2 Result     else          Do somethign else complex here       callback null   Actions ended  arg1 was  lt  from arg2       Args  1 No error  2 Result                 Call it this way      Third argument is an anonymous function with 2 args for error and result     myTest 3  6  function err  result      var resultElement   document getElementById  my result      if  err        resultElement innerHTML    Error      err      resultElement style color    red         throw err     if you want     else       resultElement innerHTML    Result      result      resultElement style color    green             and the HTML that will render the result    lt div id  my result  gt    Result will come here   lt  div gt    You can play with it here  https   jsfiddle net q8gnvcts  - for example try to pass string instead of number  myTest  some string   6  function err  result    and see the result   I hope this example helps because it represents the very basic idea of callback functions

[javascript] JavaScript: Passing parameters to a callback function

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