Question

The next code display the date every 1 sec and then stops.

(function() {
    var i = setInterval(function() {
        console.log(new Date());
    }, 1000);
    console.log("Hi");

    setTimeout(function() {
        clearInterval(i);
    }, 3000);
    console.log("Hola");
})();

Output:

Hi
Hola
Wed Oct 24 2012 13:35:27 GMT+0200 (CEST)
Wed Oct 24 2012 13:35:28 GMT+0200 (CEST)
Wed Oct 24 2012 13:35:29 GMT+0200 (CEST)

But I don’t know why Hi and Hola are displayed first. Also, why setTimeout is executed? It is not supposed that setInterval is executed every 1 sec and nothing else can be executed?. (Does the code above runs on the order in which it is written?)
Thanks.

Answer 1

setTimeout as well as setInterval only register functions (callbacks) but then go straight to the next command.

Therefor Hi and Hola are printed before the first callbacks are called.

First callback will be that of setInterval after 1 sec, then again after 2 sec.. After 3 seconds setTimeout kicks in and clears setInterval.