Javascript event handler with parameters

Question

I want to make an eventHandler that passes the event and some parameters  The problem is that the function doesn t get the element  Here is an example   doClick   function func       var elem         the element where it is all about     elem onclick   function e           func e  elem           doClick function e  element          do stuff with element and the event       The  elem  must be defined outside of anonymous function  How can i get the passed element to use within the anonymous function  Is there a way to do this   And what about addEventListener  I don t seem to be able to pass the event through an addEventListener at all do I    Update  I seemed to fix the problem with  this   doClick   function func       var that   this      this element onclick   function e           func e  that             Where this contains this element that i can access in the function   The addEventListener  But i m wondering about the addEventListener   function doClick elem  func       element addEventListener  click   func event  elem   false

User · Answer

Something you can try is using the bind method  I think this achieves what you were asking for  If nothing else  it s still very useful   function doClick elem  func      var diffElem   document getElementById  some element      could be the same or different element than the element in the doClick argument   diffElem addEventListener  click   func bind diffElem  elem      function clickEvent elem  evt      console log this     console log elem          this  and elem can be the same thing if the first parameter       of the bind method is the element the event is being attached to from the argument passed to doClick   console log evt      var elem   document getElementById  elem to do stuff with    doClick elem  clickEvent

User · Answer

I don t understand exactly what your code is trying to do  but you can make variables available in any event handler using the advantages of function closures   function addClickHandler elem  arg1  arg2        elem addEventListener  click   function e               in the event handler function here  you can directly refer            to arg1 and arg2 from the parent function arguments        false       Depending upon your exact coding situation  you can pretty much always make some sort of closure preserve access to the variables for you   From your comments  if what you re trying to accomplish is this   element addEventListener  click   func event  this elements i      Then  you could do this with a self executing function  IIFE  that captures the arguments you want in a closure as it executes and returns the actual event handler function   element addEventListener  click    function passedInElement        return function e   func e  passedInElement          this elements i    false     For more info on how an IIFE works  see these other references   Javascript wrapping code inside anonymous function  Immediately-Invoked Function Expression  IIFE  In JavaScript - Passing jQuery  What are good use cases for JavaScript self executing anonymous functions   This last version is perhaps easier to see what it s doing like this      return our event handler while capturing an argument in the closure function handleEvent passedInElement        return function e            func e  passedInElement              element addEventListener  click   handleEvent this elements i         It is also possible to use  bind   to add arguments to a callback   Any arguments you pass to  bind   will be prepended to the arguments that the callback itself will have   So  you could do this   elem addEventListener  click   function a1  a2  e           inside the event handler  you have access to both your arguments        and the event object that the event handler passes   bind elem  arg1  arg2

User · Answer

It is an old question but a common one  So let me add this one here   With arrow function syntax you can achieve it more succinct way since it is lexically binded and can be chained   An arrow function expression is a syntactically compact alternative to a regular function expression  although without its own bindings to the this  arguments  super  or new target keywords   const event handler    event  arg    gt  console log event  arg   el addEventListener  click    event    gt  event handler event   An argument       If you need to clean up the event listener      Let s use use good old function sytax function event handler event  arg      console log event  arg         Assign the listener callback to a variable var doClick    event    gt  event handler event   An argument      el addEventListener  click   doClick       Do some work        Then later in the code  clean up el removeEventListener  click   doClick     Here is crazy one-liner      You can replace console log with some other callback function el addEventListener  click    event    gt    arg    gt  console log event  arg    An argument       More docile version  More appropriate for any sane work   el addEventListener  click    event    gt    arg    gt      console log event  arg       An argument

User · Answer

this inside of doThings is the window object  Try this instead   var doThings   function  element        var eventHandler   function ev  func           if  element ev     undefined                return                     element ev    function e               func e  element                         return           eventHandler  eventHandler

User · Answer

Given the update to the original question  it seems like there is trouble with the context   this   while passing event handlers  The basics are explained e g  here http   www w3schools com js js function invocation asp  A simple working version of your example could read  var doClick   function event  additionalParameter          do stuff with event and this being the triggering event and caller    element addEventListener  click   function event      var additionalParameter          doClick call this  event  additionalParameter       false     See also Javascript call    amp  apply   vs bind

User · Answer

Short answer   x addEventListener  click   function e  myfunction e  param1  param2            function myfunction e  param1  param1

User · Answer

let obj   MyObject     elem someEvent  function    obj func param          calls the MyObject func  passing the param

[javascript] Javascript event handler with parameters

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