how can i execute the loop again after loop finish using javascript

Question

In my code i want to loop again once a certain condition if(i === arr.length) matched. here is the demo code. any idea how can i solve it?

var arr = [1,2,3];

for (let i = 0; i < arr.length; i++)
{
  setTimeout( function timer()
  {
      console.log("test");
      if(i === arr.length){
      // start the looping after this condition match
      }
  }, i*3000 );
}

I am not sure I fully understand, but you can set i=0 inside your if-statement to restart the loop — John
– John, Commented Aug 6, 2020 at 11:32
Your loop is finished before even the first test is written to the console. What are you actually trying to achieve. Essentially you've presented us an XY Problem — Jamiec
– Jamiec, Commented Aug 6, 2020 at 11:35
@RIYAL I think you should explain what you're trying to do, rather than fix what you're trying to do. I bet there's a much easier approach to you problem :) — Mick
– Mick, Commented Aug 6, 2020 at 11:38
Put the loop in a function and call that function whenever you want the loop to run — Jannes Carpentier
– Jannes Carpentier, Commented Aug 6, 2020 at 11:40
Also your if statement is never true since i will have values 0 1 2 and arr.length is 3 — Jannes Carpentier
– Jannes Carpentier, Commented Aug 6, 2020 at 11:41

Menawer · Accepted Answer · 2020-08-06 11:41:08Z

Your code never reaches the condition since i < arr.length is your exit, if you change it to i <= arr.length then the condition will be reached,

then to re-enter the loop i suggest that you encapsulate all your loop in a function

var arr = [1,2,3];

for (let i = 0; i < arr.length; i++)
{
  setTimeout( function timer()
  {
      console.log("test");
      if(i === arr.length){
      // start the looping after this condition match
      }
  }, i*3000 );
}

To

var arr = [1,2,3];

function Looper(){
   for (let i = 0; i <= arr.length; i++)
   {
     setTimeout( function timer()
     {
         console.log("test");
         if(i === arr.length){
             Looper();
         }
     }, i*3000 );
   }
}

Looper();

Keep in mind that this is an infinite loop, you would better use setInterval, if thats your goal, but if you have something else in mind hope this helps.

Jamiec · Accepted Answer · 2020-08-06 11:44:56Z

The problem with your code as it is now is the loop is exited before even the first setTimeout call back runs. The addition of a console.log after the loop confirms this.

var arr = [1,2,3];

for (let i = 0; i < arr.length; i++)
{
  setTimeout( function timer()
  {
      console.log("test");
      if(i === arr.length){
      // start the looping after this condition match
      }
  }, i*3000 );
}
console.log("Loop exited");

So there is no way to restart that loop. However you can re-organise your code to keep looping over your arr with a 3000ms delay. The easiest is probably with a Promise.

var arr = [1,2,3];

async function doWork(item){
    return new Promise(resolve => {
        setTimeout(() => {
            console.log("finished",item); // do whatever you want to do here
            resolve();
        },3000);
    });
}


async function test(){
  var exit = false; // if you set this to true elsewhere the code will stop
  var i = 0;

  while(!exit){
    var item = arr[i++ % arr.length];
    await doWork(item);
  }
}

test();

Linux Torvalds · Accepted Answer · 2020-08-06 11:48:25Z

0

Here is simple attempt hope you'll find it helpful

var arr = [1, 2, 3];
var i = 0;

var i = 0;

function timer() {
  console.log(arr[i])
  i = (i + 1) % arr.length;
}
setInterval(timer, 1000);

answered Aug 6, 2020 at 11:48

Linux Torvalds

4,1293 gold badges24 silver badges49 bronze badges

Collectives™ on Stack Overflow

how can i execute the loop again after loop finish using javascript

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related