$('#start') executes the function myFunction() and $('#stop') end it. How do I stop myFunction() from executing?
function myFunction() { $(document).mousemove(function(e) { $('#field').html(e.pageY) }); } $('#start').click(function() { myFunction(); }); $('#stop').click(function() { //stop myFunction }); As Daniel pointed out, you actually want to unbind the event handler. You can use unbind for this:
$('#stop').click(function() { $(document).unbind('mousemove'); }); But this will also remove all other mousemove event handlers, that might be attached by other plugins or similar (I mean, you attach to the document element not a "custom" element, so it can be that other JavaScript code also binds handlers to this element).
To prevent this, you can use event namespaces. You would attach the listener with:
function myFunction() { $(document).bind('mousemove.namespace', function(e) { $('#field').html(e.pageY); }); } and unbind:
$('#stop').click(function() { $(document).unbind('mousemove.namespace'); }); This would only remove your specific handler.
You want to use the jQuery bind and unbind methods. For example:
function myFunction() { $(document).mousemove(function(e) { $('#field').html(e.pageY) }); } $('#start').bind('click.myFunction', function() { myFunction(); }); $('#stop').bind('click', function() { $('#start').unbind('click.myFunction'); }); 
You're not stopping the function from executing. Your myFunction() simply attaches a callback to an event listener, which is called whenever the mouse is moved on the document. The callback function is invoked and is terminated immediately.
You'd simply want to unbind the callback from the event listener. Check out the other answers for concrete examples.
A better way would be to use bind and unbind, like so:
function myFunction() { $(document).mousemove(function(e) { $('#field').html(e.pageY) }); } $('#start').bind('click', myFunction); $('#stop').click(function() { $('#start').unbind('click', myFunction); }); 
bind('click', myFunction), not bind('click', myFunction()). Similar for unbind.