I can't change global variable inside setInterval es6

Question

I have to find a button when it will appear. In order to do that I use setInterval. When it finds this button, it gives to my variable needed value. I check it inside the setTimeout, but after setTimeout(outside these method) my global variable became as before setTimeout. How to fix that?

let foundValue;
function findById(id) {
  let interval = setInterval(() => {
    if (document.getElementById(id)){
      let foundValue = document.getElementById(id);
      clearInterval(interval);
    }
  }, 1000);
  return foundValue;
}

Essentially, you have two variables in different scopes called the same thing — Liam, Nov 07 '16 at 16:59
Are you checking `foundValue` after the interval, or are you checking the value returned by `findById`, because the way you `return` there is unlikely to be what you want. — loganfsmyth, Nov 07 '16 at 17:35
I found that I return before setinterval found button, but how should i wait for end of interval? — teimurjan, Nov 07 '16 at 17:46
@TeymurGasanov You [cannot wait and `return`](http://stackoverflow.com/q/14220321/1048572) — Bergi, Nov 07 '16 at 18:32

score 1 · Accepted Answer · answered Nov 07 '16 at 17:00

1

It's because you're re-declaring foundValue inside setInterval so you should remove the second let, for example:

let foundValue;
function findById(id) {
  let interval = setInterval(() => {
    if (document.getElementById(id)){
      foundValue = document.getElementById(id);
      clearInterval(interval);
    }
  }, 1000);
  return foundValue;
}

answered Nov 07 '16 at 17:00

phpchap

382
2
7

I deleted these let but nothing happened – teimurjan Nov 07 '16 at 17:27
It's working for me as follows `console.log(foundInterval) // is undefined` then `findById('element_id')` then `console.log(foundInterval) // contains element` – phpchap Nov 07 '16 at 18:18

I can't change global variable inside setInterval es6

1 Answers1