JavaScript setTimeout in Object

Question

I am trying to give an object a countdown timer and when the countdown is down it should call a function which removes this object from an array.

array = [];

var object = {
    'name' : 'user',
    'limit' : function() {
         setTimeout(destroyMe(this),10000);
    }
}

array.push(object);

var destroyMe = function(obj) {
    array.remove(obj);
}

I know that there could a problem with the this but the timeout function doesnt work at all not even like this:

var object = {
    'name' : 'user',
    'limit' : function() {
               setTimeout(console.log("dd"),3000);
            }
}

Maybe someone can tell me the issue with my version of the setTimeout. thx

`[].remove`? Never heard of it. And you need to do a `array[0].limit()` to initiate the countdown. — Salman A, Dec 30 '12 at 23:20

score 7 · Accepted Answer · answered Dec 30 '12 at 23:18

7

setTimeout takes a reference to a function. The code you have is calling the function.

This should be changed to:

var object = 
{
    'name' : 'user',
    'limit' : function() 
    {
        setTimeout(function() { destroyMe(this); }, 10000);
    }
}

(You may have issues using this in this context, try it!)

var object = 
{
    'name' : 'user',
    'limit' : function() 
    {
        setTimeout( function() { console.log("dd"); },3000);
    }
}

answered Dec 30 '12 at 23:18

Lee Taylor

7,761
16
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2

`this` will be the global object. He needs to use some other variable pointing to the correct object. – ThiefMaster Dec 30 '12 at 23:27
first thing's first, call `array[0].limit();` somewhere. – Salman A Dec 30 '12 at 23:28
I was hoping that the Timout function would call itself after 3 seconds! But it doesnt if i use the code above! – user1354743 Dec 30 '12 at 23:28
@user1354743 Are you calling object's `limit` function? – Lee Taylor Dec 30 '12 at 23:34
No I am not....I was hoping after the 10 seconds the it will be called by itself without me calling limit! – user1354743 Dec 30 '12 at 23:39
@user1354743 `limit` is a function. What other functions automatically run themselves without the programmer's intervention? – Lee Taylor Dec 30 '12 at 23:40
alright I understand that ...but is there a way that it would work as I wanted it? ... for example: once the object is created the countdown starts and after 3 seconds it will execute the function!??? – user1354743 Dec 30 '12 at 23:45
1

@user1354743: Just put the `setTimeout` call *after* the object. – Felix Kling Dec 30 '12 at 23:58
thats exactly what I wanted! Thx – user1354743 Dec 31 '12 at 00:18
'limit' : setTimeout(destroyMe(this),10000) – user1354743 Dec 31 '12 at 00:30
1

@user1354743 - No, that won't work. You're calling the function, not passing a reference to a function. – Lee Taylor Dec 31 '12 at 00:37

score 1 · Answer 2 · answered Dec 30 '12 at 23:18

You need to pass a function to setTimeout, not a function call.

var object = {
    'name' : 'user',
    'limit' : function() {
         setTimeout(function() { 
             destroyMe(this)
         }, 10000);
    }
};

As you already know, the this probably doesn't do what you are expecting. Replacing destroyMe(this) with console.log("dd") should result in a behavior that you would expect.

score 1 · Answer 3 · edited May 23 '17 at 12:12

1

setTimeout either takes a callback (a function, not a function call with arguments) or code in quotes. However, as noted in this question, passing a string is only allowed for historical reasons--there aren't any good reasons for doing it in practice.

But, for completeness sake, one way to do what you want is:

var object = {
    'name' : 'user',
    'limit' : function() {
               setTimeout('console.log("dd")', 3000);
            }
}

edited May 23 '17 at 12:12

Community

1
1

answered Dec 30 '12 at 23:23

Robz

1,747
5
21
35

Please do not suggest passing a string. Ever. There is just not a single acceptable reason to do pass a string instead of a function. Besides that he needs `this` to be preserved. – ThiefMaster Dec 30 '12 at 23:25
If mentioning the string passing, you *must* IMO also warn that it's a pretty terrible way to do things. – alex Dec 30 '12 at 23:28

JavaScript setTimeout in Object

3 Answers3