Question

Let’s say we have this:

function myMethod1() {
    ...
}

and later in the code:

myMethod1();
alert('myMethod1() was executed!');

I need to set timeout for the alert so that it will be called after myMethod1() executes. But how do I know the value of the second parameter for the setTimeout function? How do I measure the time needed for myMethod1() to execute?

MyMethod1() has an async ajax call.

Answer 1

If your method performs an asynchronous task, it’s common to pass a callback function like so:

function myMethod(cb)
{
    // some code, such as $.ajax
    $.ajax({
         url: 'example.com',
         complete: function() {
             // we're done, notify callback
             cb();
         }
    });
}

Then, cb is passed in like this upon execution:

myMethod(function() {
    alert('method is done');
});
alert('method returned, but is still doing stuff in the background');

This is the mantra of asynchronous design; every method that performs a task in the background will have some way of notifying a callback function of its completion.

---

If the method is synchronous however, you could call cb() at the end of the function body, but it would be much easier to keep what you had:

myMethod();
alert('method is done');