The timeout mechanism can be used to defer the execution of a block of script code. You can defer several blocks at once if necessary, so there could be a number of pending timeout triggers. You must be able to identify the one that you want to clear.

When you create a timeout trigger with the setTimeout() method, it will return back to you with a value that corresponds uniquely to that trigger's set-up context. You can use that value later to clear the timeout trigger.

You must be careful not to clear timeout triggers more than once.

Warnings:

• Be careful when clearing interval timers. If you try to clear one that does not exist, it can sometimes crash the browser.

• It is highly likely that the interval may have elapsed and the timeout no longer exists to be cleared. A more reliable technique that is less prone to browser crashes is to set a flag value in a global variable and then test that from within the timeout invoked function.