CODEWITHSUNDEEP
angulartypescript
Manu Chadha
Manu Chadha

Reputation: 16723

why adding keyword `let` or `var` makes code uncompilable

In following component class, if I add let keyword, the code doesn't compile. Why?

export class HelloComponent {
  @Input() name: string;
  name2:string;//let name2:string doesn't compile.

  constructor(){

  }
}

Upvotes: 2

Views: 188

Answers (2)

Günter Zöchbauer
Günter Zöchbauer

Reputation: 657526

let and var are only required/allowed for local variables, not for class fields.

export class HelloComponent {
  @Input() name: string;
  name2:string;//let name2:string doesn't compile.

  constructor(){
    var x = 5; // ok
    let y = 5; // ok
    const z = 5; // ok
  }
}

In a class outside a method (or constructor) only variable initialization and method declaration is allowed, therefore let is redundant and therefore not allowed.

Upvotes: 5

user4676340
user4676340

Reputation:

Because you are in a class : 

export class HelloComponent

In a class, you declare properties/members that will be accessible like this

let hello = new HelloComponent();
console.log(hello.name2); // In your case, shows "undefined"

This an object property.

For var and let, you create block-scoped variables : those are variables that will die once you leave the block of code you're in, such as a function.

Upvotes: 3

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