Angular 2 update class with setTimeout

Question

I'm trying to add a class to an element and remove it after a certain time using setTimeout.

Component

export class setClass implements OnInit {
  className: string = ''

  setClassName(newClass) {
    this.className = newClass

    setTimeout(function () {
      this.className = ''
    }, 1500)
  }

  constructor() { }

  ngOnInit() {
  }
}

Template

<div>
    <img src="img/1.png" alt="" [ngClass]="className">
    <button (click)="setClassName('foobar')">Set new class</button>
</div>

I can see the function adds the class name 'foobar' but it stays forever. I'm expecting this function to remove the newly added after 1500ms.

Please help me fix this.

score 1 · Accepted Answer · answered Mar 08 '17 at 20:30

Your this line this.className = newClass the this is pointing to the component but the this inside timeout is pointing to the window use ES6 to ignore this

setTimeout(() => {
  this.className = "";
}, 1500);

Or store instance of this to vm

let vm = this;
setTimeout(function() => {
  vm.className = '';
}, 1500);

both are working fine.

score 0 · Answer 2 · answered Mar 08 '17 at 20:24

0

'this' is not defined in your timeout function because of function scope and you'll not be able to use it. You can use an arrow function like this:

setTimeout(()=> {
      this.className = ''
    }, 1500)

answered Mar 08 '17 at 20:24

Тодор Иванов

381
3
18

El houcine bougarfaoui · Answer 3 · 2017-03-08T20:38:28.390

0

<div>
    <img src="img/1.png" #image alt="">
    <button (click)="setClassName('foobar')">Set new class</button>
</div>

export class setClass implements OnInit {
  className: string = ''
  @ViewChild("image") image ;
  setClassName(newClass) {
    this.image.nativeElement.classList.add(newClass)
    let self = this;
    setTimeout(function () {
      self.image.nativeElement.classList.remove(newClass)
    }, 1500)
  }

  constructor() { }

  ngOnInit() {
  }
}

edited Mar 08 '17 at 20:38

answered Mar 08 '17 at 20:28

El houcine bougarfaoui

32,617
9
35
35

I suspect you will get cannot call classList of undefined – yurzui Mar 08 '17 at 20:31
I updated my solution @yurzui , it works fine. – El houcine bougarfaoui Mar 08 '17 at 20:35
'this.image' will still be undefined in the setTimeout function – Тодор Иванов Mar 08 '17 at 20:37
sorry see the update – El houcine bougarfaoui Mar 08 '17 at 20:38

score 0 · Answer 4 · answered Mar 08 '17 at 21:11

0

Change it to the code below and it will work. Also, have a plunker https://plnkr.co/edit/oEfZOW?p=preview that shows it working

let $this = this;
setTimeout(function () {
    $this.className = '';
}, 1500);

answered Mar 08 '17 at 21:11

nekkon

107
6

Angular 2 update class with setTimeout

4 Answers4