Question

In a simple setInterval

setInterval(function() {
      // Do something every 9 seconds
}, 9000);

The first action will happen after 9 seconds (t=9s). How to force the loop to perform the first action immediately (t=0)?

I think it is due to the mechanism of setInterval to have Delay - Action - Delay - Action ... loop; instead of Action - Delay - Action - Delay ... loop.

EDIT: My function is indeed a loop as

setInterval(function(){
$('.test').each(function(idx){
    var duration = 1000;
    $(this).delay(duration*idx);
    Some stuff here
});
}, 4000);

Answer 1

Keep it simple. You can use a named function instead of an anonymous function; call it and set an interval for it.

function doSomething() {
    console.log("tick");
}
doSomething();
setInterval(doSomething, 9000);

Create a scope if necessary:

(function() {
    function doSomething() {
        console.log("tick");
    }
    doSomething();
    setInterval(doSomething, 9000);
})();

Finally, the following works without creating or affecting x:

setInterval(function x() {
    console.log("tick");
    return x;
}(), 9000);