Creating a TypeScript class with null properties upon initialization

Question

Creating a TypeScript class with null properties upon initialization

Recently, I kicked off a fresh Next.js project using TypeScript by running

npx create-next-app --example with-typescript with-typescript-app

(https://github.com/zeit/next.js/tree/master/examples/with-typescript).

However, when attempting to define a class like this:

export class Programm {
    id: string;
    name: string;
    thumbnailUrl: string;
}

I encountered a syntax error saying:

Property 'id' has no initializer and is not definitely assigned in the constructor.ts(2564)

The issue was resolved when I added a constructor as follows:

constructor(id: string, name: string, thumbnailUrl: string) {
    this.id = id;
    this.name = name;
    this.thumbnailUrl = thumbnailUrl;
}

Why does this happen and how could I initialize the properties to be null while creating an object of the class?

Interestingly, the same code works fine in Angular without the need for the constructor.

typescript

Answer 1

Answer №1

To make properties optional in TypeScript, simply add a ? after the property name:

export class Programm {
     id?: string;
     name?: string;
     thumbnailUrl?: string;
}

When you create an instance of type "Programm", these optional properties will default to undefined.

Answer 2

To make properties optional in TypeScript, simply add a ? after the property name:

export class Programm {
     id?: string;
     name?: string;
     thumbnailUrl?: string;
}

When you create an instance of type "Programm", these optional properties will default to undefined.

Answer 3

Answer №2

If you want to achieve a solution, you may consider the steps outlined below: -> First, refer to @Mr.Jurica Smircic's resolution and -> Define an Initial Value

constructor(id: string, name: string, thumbnailUrl: string) {
    this.id = id || '' ;
    this.name = name || '';
    this.thumbnailUrl = thumbnailUrl || '';
}

The topic of whether or not to use null or undefined is heavily debated in various discussions on Stack Overflow. It is generally recommended to establish initial values either through the constructor or at object initialization, such as with an empty object. For further insight, you can explore the following Q&A threads. Thank you

Answer 4

If you want to achieve a solution, you may consider the steps outlined below: -> First, refer to @Mr.Jurica Smircic's resolution and -> Define an Initial Value

constructor(id: string, name: string, thumbnailUrl: string) {
    this.id = id || '' ;
    this.name = name || '';
    this.thumbnailUrl = thumbnailUrl || '';
}

The topic of whether or not to use null or undefined is heavily debated in various discussions on Stack Overflow. It is generally recommended to establish initial values either through the constructor or at object initialization, such as with an empty object. For further insight, you can explore the following Q&A threads. Thank you

Answer 5

Answer №3

When initializing your variables, it is possible to set them as null instead of undefined by following this method:

export class Project {
    id: string | null = null;
    title: string | null = null;
    imageUrl: string | null = null;
}

let project = new Project()
console.log(project)

>>> Project: { "id":null, "title":null, "imageUrl":null }

Answer 6

When initializing your variables, it is possible to set them as null instead of undefined by following this method:

export class Project {
    id: string | null = null;
    title: string | null = null;
    imageUrl: string | null = null;
}

let project = new Project()
console.log(project)

>>> Project: { "id":null, "title":null, "imageUrl":null }

Creating a TypeScript class with null properties upon initialization

Answer №1

Answer №2

Answer №3

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