CODEWITHSUNDEEP
javascriptangular
Aaron Rabinowitz
Aaron Rabinowitz

Reputation: 357

angular 4 not able to push on an array of undefined

I am trying to push on an array for every interval but for some reason I get an error either it is ERROR TypeError: Cannot set property 'NaN' of undefined if I use this.numbers[this.value] = this.value; or it is core.es5.js:1020 ERROR TypeError: Cannot read property 'push' of undefined if I use this.numbers.push(this.value);

here is my code

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-game-control',
  templateUrl: './game-control.component.html',
  styleUrls: ['./game-control.component.css']
})
export class GameControlComponent implements OnInit {
  timer = null;
  value: number;
  interval: number;
  numbers = [];


  constructor() { }


  ngOnInit() {
      console.log(this.numbers);
  }

  onClickStart() {
    console.log('timer called');
    if (this.timer !== null) {
      return;
    }
    this.timer = setInterval(function() {
      this.value += 1;
      // console.log(this.numbers[this.value - 1 ]);
      // this.numbers[this.value] = this.value;
      this.numbers.push(this.value);
      console.log(this.numbers);
    }, this.interval );
  }

  onClickStop() {
    clearInterval(this.timer);
    this.timer = null;
  }

}

My html is 

<div class="row">
          <div class="col-xs-12 "> 
            <button type="submit" class="btn btn-success" (click)="onClickStart()">Start</button>
            <button type="button" class="btn btn-danger" (click)="onClickStop()">Stop</button>
            <button type="button" class="btn btn-primary" >Clear</button>
          </div>
</div>
<div class="row">
  <div class="col-xs-10">

  <hr>
  <ul class="list-group">
    <a 
      class="list-group-item" 
      style="cursor: pointer"
      *ngFor="let number of numbers"
      >
      <app-even [num]="number" ></app-even>
      <app-odd [num]="number" ></app-odd> 
    </a>
  </ul>
  </div>
</div>

but I don't think it matters yet

Upvotes: 0

Views: 467

Answers (1)

G&#252;nter Z&#246;chbauer
G&#252;nter Z&#246;chbauer

Reputation: 657416

function () {} causes this not to point to the current class instance anymore, as most coming from other languages would expect, use arrow functions instead to get the desired behavior:

this.timer = setInterval(() => {

Upvotes: 4

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