How do i maintain the value of the loop variable in a setTimeout? Javascript

Question

Basically, i have a loop where if a certain condition is met, it fires a setTimeout. But the timeout function requires the value of the loop ( i.e 'i'), as example below. How do i do that?

 for( var i = 0; i <= 10; i++) {
    if(something){
      setTimeout(function(){
         console.log(i);
      }, 1000);
    }
 }

FYI, modern browsers let you pass extra arguments to `setTimeout` which show up as callback arguments. `setTimeout(function(i) { console.log(i); }, 1000, i);` — , Jan 02 '16 at 17:34

score 2 · Accepted Answer · answered Jan 02 '16 at 17:31

2

Use IIFE (immediately-invoked function expression), it is a JavaScript design pattern which produces a lexical scope using JavaScript's function scoping.

 for( var i = 0; i <= 10; i++) {
    if(something){
        (function(i){
            setTimeout(function(){
               console.log(i);
            }, 1000);
         })(i);
     }
 }

answered Jan 02 '16 at 17:31

void

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Thank you, learned something new – Pratish Shrestha Jan 02 '16 at 17:36
sure, "You can accept the answer in 5 mins." – Pratish Shrestha Jan 02 '16 at 17:38
@user3783888: Do you understand the cause of the initial problem and how the solution works? – Jan 02 '16 at 17:50
yes, i think.. as the value of i changes when the timeout function calls it. So, when it is immediately invoked the current value of i is passed in that function.. right? or smth else – Pratish Shrestha Jan 03 '16 at 06:08

score 0 · Answer 2 · answered Jan 02 '16 at 17:31

0

for (var i = 0; i <= 10; i++) {
  if (true) {
    setTimeout((function(i) {
     return function() { console.log(i); }
    })(i), 1000 * i);
  }
}

and I think you want the time to be 1000 * i ? (It's already in the code above)

answered Jan 02 '16 at 17:31

CoderPi

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How do i maintain the value of the loop variable in a setTimeout? Javascript

2 Answers2