When null is assigned to a type in Typescript, it does not result in an error being triggered

Could someone enlighten me on why this code is not causing an error?

import { Injectable } from '@angular/core';

interface Animal{
  name: string;
}

@Injectable()
export class AnimalService {
  lion: Animal = null;
  constructor() {}
  get(){
   return this.lion;
 }
}

Answer №1

Make sure to configure your tsconfig.json file with "strictNullChecks": true in order for errors to be thrown when attempting to assign null to a variable like lion: Animal = null;.

Refer to the documentation regarding the strictNullChecks compiler flag:

When using strict null checking mode, null and undefined values can only be assigned to themselves or any (with the exception of undefined being also assignable to void).

For more information, visit:

Answer №2

In certain scenarios where null values are permissible, implement the syntax variable: Type | null.

For example: age: number | null

I prefer to enable strictNullChecks and apply this approach in my codebase.

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