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event handlers by jaredn
Posted: 18 Dec 00

in Javascript, to associate a given function with an event via script, you must use syntax like this:

     //do something

window.document.body.onclick = someFunc

The important thing to note is that in the line above, there are no ()'s after someFunc. The reasoning behind this is, javascript will execute whatever is on the right of the equals sign, this is because in JS, functions can be treated ad data. Suppose you wanted to pick a random event handler for your onclick event. You could use something like this:

function randomHandler()
     //do something and define rndmhdnler as
     //a function reference
     return rndmhdnler

window.document.body.onclick = randomHandler()

it immediately, before any click occurs (whenever the intrepreter first sees the line above) runs randomHandler and returns a function reference.

This is just an example of one event handler you can register.So remember don't use ()'s unless you want the code to be run immediately.

Note: Above applies only when setting the events in a script block. If you define them inline like:

<img onmouseover="someFunc()">

notice the ()'s are there - strange, but that's just the way it is.

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