Capturing events in javascript
https://stackoverflow.com/questions/9022922
-
19-04-2021 - |
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<!doctype html>
<html>
<body>
<div id = 'div' style = 'width:100px;height:100px;background:#000000;'></div>
<script type = 'text/javascript'>
document.getElementById('div').addEventListener('click',happen(),true);
function happen()
{
alert(1)
}
</script>
</body>
</html>
In the above code why the event is triggered when the page loads and not triggered when i click on the div...Also which is the correct event name click or onclick....
Solution
It's because you've immediately called the function, and passed its null result to addEventListener().
It should be:
document.getElementById('div').addEventListener('click',happen,true);
If you want to pass arguments to happen, you'd have to write this:
document.getElementById('div').addEventListener('click', function() {
happen(args_here, ...);
}, true);
OTHER TIPS
You're calling the function immediately and passing its return value to addEventListener, just like any other function call.
Take out the ().
This should work:
document.getElementById('div').addEventListener('click',happen,true);
The problem is with this line:
document.getElementById('div').addEventListener('click',happen(),true);
You should should only be passing the name of the function happen but since you added the parentheses, you are passing the result.
Try this instead:
document.getElementById('div').addEventListener('click',happen,true);
As the other answerers have said, taking out the () will fix the problem.
An alternative, and a good practice for OO Javascript, is to wrap the function inside a function(){ }, like so:
document.getElementById('div').addEventListener('click',function(){happen()},true);
That will retain scope if the callback needs to execute within an object (in this case it does not).
The event handler does not need parenthesis
document.getElementById('div1').addEventListener('click',happen,true);
