how to change onclick event with jquery?

You can easily change the onclick event of an element with jQuery without running the new function with:

$("#id").attr("onclick","new_function_name()");

By writing this line you actually change the onclick attribute of #id.

You can also use:

document.getElementById("id").attribute("onclick","new_function_name()");

Remove the old event handler

$('#id').unbind('click');

And attach the new one

$('#id').click(function(){
    // your code here
});

Updating this post (2015) : unbind/bind should not be used anymore with jQuery 1.7+. Use instead the function off(). Example :

$('#id').off('click');
$('#id').click(function(){
    myNewFunction();
    //Other code etc.
});

Be sure that you call a non-parameter function in .click, otherwise it will be ignored.

$('#id').attr('onclick', 'function()');

Right now (11 Jul 2015) this solution is still working (jquery 2.1.4); in my opinion, it is the best one to pick up.

If you want to change one specific onclick event with jQuery, you better use the functions .on() and .off() with a namespace (see documentation).

Use .on() to create your event and .off() to remove it. You can also create a global object like g_specific_events_set = {}; to avoid duplicates:

$('#alert').click(function()
{
    alert('First alert!');
});

g_specific_events_set = {};

add_specific_event = function(namespace)
{
    if (!g_specific_events_set[namespace])
    {
        $('#alert').on('click.' + namespace, function()
        {
            alert('SECOND ALERT!!!!!!');
        });
        g_specific_events_set[namespace] = true;
    }
};

remove_specific_event = function(namespace)
{
    $('#alert').off('click.' + namespace);
    g_specific_events_set[namespace] = false;
};



$('#add').click(function(){ add_specific_event('eventnumber2'); });

$('#remove').click(function(){ remove_specific_event('eventnumber2'); });

div {
  display:inline-block;
  vertical-align:top;
  margin:0 5px 1px 5px;
  padding:5px 20px;
  background:#ddd;
  border:1px solid #aaa;
  cursor:pointer;
}
div:active {
  margin-top:1px;
  margin-bottom:0px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<div id="alert">
  Alert
</div>
<div id="add">
  Add event
</div>
<div id="remove">
  Remove event
</div>