更改复选框的值不会触发Jquery中的更改事件

Question

I have a checkbox and I marked it as checked, however it doesnt fire the on change function. The note doesn't appear.

My code:
 $('#checkbox1').prop("checked", true);

$('#checkbox1').change(function(){
        if ($(this).is(':checked'))
            $('#s-note').show();
        else
            $('#s-note').hide();
    });

Answer 1

If you are setting the note to be hidden by default and doing it with an id based selector, like this:

#s-note { display:none; }

Then your code won't be able to show it because it also uses an id based selector and that won't be more specific than the selector already in effect.

Instead, you'll have to default the note to hidden using a selector that is less specific than the id selector you will use to show/hide it later. That would be a class.

Also, it's critical that you set up the event handler before you trigger the event, so that when the event happens, there is already an event handler registered.

Now, for your needs, you don't really need the change event, click will do just fine. And, lastly, to ensure that you properly trigger the event, use JQuery's .trigger() method to set things in motion.

 // Make sure you set up the callback first $('#checkbox1').on("click", function(){ if ($(this).is(":checked")) $('#s-note').show(); else $('#s-note').hide(); }); // Then just trigger the event $('#checkbox1').trigger("click"); 

 .hide { display:none; } 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input type="checkbox" id="checkbox1">Test <div id="s-note" class="hide">Special</div> 

Answer 2

Do you expect the onchange to fire without user interaction?

Your issue is you set the checked state before you set the handler so if this would have trigged change, you would have not caught it. Your real issue here is setting the property with JavaScript does not fire the change event. So you need to trigger the change event manually.

$('#checkbox1')
  .prop("checked", true)  // set it to checked
  .on("change", function() {  // bind change event
    $('#s-note').toggle($(this).is(':checked')); // toggle visibility
  }).trigger("change"); //trigger that you need the change to run

Answer 3

I hope this code snippet will help you

Approach 1
$('#idcheckbox').on('change', function() {
  if($(this).is(':checked')) {
    alert('checked');
  } else {
   alert('default ');
  }
});

Approach 2
$('input[type=checkbox]').on('change', function() {
if($(this).is(':checked')) {
    alert('checked');
  } else {
   alert('default ');
  }
});

Answer 4

I ran your code in .net mvc and it runs fine.

This is the checkbox same id it hide or shows div element.

<input type="checkbox" id="checkbox1" value=" " />
<div id="s-note" style="display: none">
       <label>Showing</label>
</div>

What are you trying to display?