Which is better in Angular2: defining default property values in the constructor or inline?

When it comes to creating an object class in Angular 2, the common dilemma is whether to initialize values inline or within a constructor. But what exactly is the difference between the two approaches?

export class Foo {
  id: string;
  name: string = '';
  url: string = '';
}

versus

export class Foo {
  id: string;
  name: string;
  url: string;

  constructor() {
    this.name = '';
    this.url = '';
  }
}

Answer №1

There is no variance in the JavaScript produced between the pair. During TypeScript compilation, the compiler simply incorporates values that are initialized inline within the constructor.

Test it for yourself: https://www.typescriptlang.org/play/

Answer №2

There are two main methods for initializing properties in JavaScript: inline and in the constructor. Initializing a property inline provides conciseness and keeps the default value of the property in context with its declaration.

On the other hand, initializing a property in the constructor allows you to utilize constructor parameters when setting the property values. This method also enables you to separate the order of declaration from the order of initialization, especially useful when one property's starting value depends on another one's.

Your choice between these two methods, when not requiring the flexibility offered by the constructor, will likely come down to personal style preference.

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