[SOLVED] Getting undefined object error in Typescript using Angular

Issue

So I am following the Traversy Media new [Angular crash course]: https://www.youtube.com/watch?v=3dHNOWTI7H8 around 39:45 and getting object undefined errors constantly.

Here is the picture of the error which says object is possibly ‘undefined’:
object is possibly ‘undefined

This worked in task-item.component.html

<p *ngFor="let task of tasks">
  {{task.text}}
</p>

This object is possibly ‘undefined’ task-item.component.html

<div class="task">
    <h3>{{task.text}}</h3>
    <p>{{task.day}}</p>
</div>

task-item.component.ts

import { Component, OnInit, Input } from '@angular/core';
    import {Task} from 'src/Task';
    
    @Component({
      selector: 'app-task-item',
      templateUrl: './task-item.component.html',
      styleUrls: ['./task-item.component.css']
    })
    export class TaskItemComponent implements OnInit {
      @Input() task?: Task;
    
      constructor() {
      }
    
      ngOnInit(): void {
      }
    
    }

I have put a tsconfig.json rule "strictPropertyInitialization": false

Solution

It’s because you set it as a an optional using ?

You can either remove ? which is not a good practice if your item can be null, or you can just do this in the html

<div class="task">
  <h3>{{task?.text}}</h3>
  <p>{{task?.day}}</p>
</div>

It will display the value if the variable is initialized, and don’t throw an error

Answered By – Alann

Answer Checked By – Candace Johnson (BugsFixing Volunteer)