set time out not working with function

Question

I am using the following to pause the javascript for a few seconds:

 setTimeout(start_countdown(),3000);

It does not work, the function is

Answer 1

If you dont need to pass params dont use ()

setTimeout(start_countdown,3000);

If you do you have to wrap your function

setTimeout(function(){start_countdown(parameter)},3000);

Answer 2

You need to pass a function reference. You are passing a function's return value.

The difference is this: one is a blueprint of the function you want to happen, the other means you are executing the function immediately and passing its return value to setTimeout.

setTimeout(start_countdown, 3000);

If you want to do something more complex than simply call a named function, OR you want to pass a param to the named function, you'll need to instead pass an anonymous function to the timeout and call your function within that:

setTimeout(function() {
    start_countdown(/* possible params */);
    /* other code here as required */
}, 3000);

Answer 3

In different browsers it works in different way. In IE you need to use the anonymous function to pass the parameters to the callback:

setTimeout(function(){alert('hi')},3000);

Answer 4

write instead

setTimeout(start_countdown, 3000);

without parens ()
the second example could be also written as

setTimeout(function() { alert('hi'); }, 3000);