Assign Click Handlers In For Loop

I'm having several div's #mydiv1, #mydiv2, #mydiv3, ... and want to assign click handlers to them: $(document).ready(function(){ for(var i = 0; i < 20; i++) { $('#question

Solution 1:

It's a common mistake to create closures in loops in Javascript. You need to have some sort of callback function like this:

function createCallback( i ){
  return function(){
    alert('you clicked' + i);
  }
}

$(document).ready(function(){
  for(var i = 0; i < 20; i++) {
    $('#question' + i).click( createCallback( i ) );
  }
});

---

Update June 3, 2016: since this question is still getting some traction and ES6 is getting popular as well, I would suggest a modern solution. If you write ES6, you can use the let keyword, which makes the i variable local to the loop instead of global:

for(let i = 0; i < 20; i++) {
  $('#question' + i).click( function(){
    alert('you clicked ' + i);
  });
}

It's shorter and easier to understand.

Solution 2:

To clarify, i is equal to 20 because the click event won't have fired until after the loop has finished.

Solution 3:

$(document).ready(function(){
  for(var i = 0; i < 5; i++) {
   var $li= $('<li>' + i +'</li>');
      (function(i) {
           $li.click( function(){
           alert('you clicked ' + i);
         });
      }(i));
      $('#ul').append($li);
  }
});

Solution 4:

Using on to attach the 'click' handler you can use the event data in order to pass your data like in:

for(var i = 0; i < 20; i++) {
  $('#question' + i).on('click', {'idx': i}, function(e) {
    alert('you clicked ' + e.data.idx);
  });
}

//
// let's creat 20 buttons
//

for(var j = 0; j < 20; j++) {
	$('body').append($('<button/>', {type: 'button', id: 'question' + j, text: 'Click Me ' + j}))
}

//
// Passing data to the handler
//
for(var i = 0; i < 20; i++) {
  $('#question' + i).on('click', {'idx': i}, function(e) {
    console.log('you clicked ' + e.data.idx);
  });
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Solution 5:

You can get by with assigning the click handler once (or at least not making many unnecessary closures). Put all the divs in one class mydivs, then:

$(document).ready(function(){
    $('.mydivs').click(function(){
        // Get the number starting from the ID's 6th character
        // This assumes that the common prefix is "mydiv"
        var i = Number(this.id.slice(5));

        alert('you clicked ' + i);
    });
});

This looks at the element's ID to get its number, using the slice string method to strip the initial letters off.

Note: It may be better to use

$('#divcontainer').on('click', '.mydivs', function(){

instead of

$('.mydivs').click(function(){