什么是枚举的 TypeScript 类型

Question

I am wondering what is the type of an enum? In my example I need to reference my Direction enum in my template. I am doing this by assigning the Direction enum to the direction variable I have exposed in my component. This variable is currently type any but I want to be more specific. What should this type be?

<!-- component.html -->
<p [ngSwitch="getDirection()"]>
    <span *ngSwitchCase="direction.NORTH">Heading North</span>
    <span *ngSwitchCase="direction.EAST">Heading East</span>
</p>


// component.ts
enum Direction {
  NORTH,
  EAST,
  SOUTH,
  WEST
}
direction: any; // <-- what should this type be?
constructor() {
  this.direction = Direction;
}

Answer 1

direction$: typeof Direction;

Should be ok.

But actually you do not need this. You may let typescript to infer this type:

enum Direction { NORTH, EAST, SOUTH, WEST }

class MyComponent {
  readonly direction$ = Direction;
  constructor() {
    //...
  }
}

There is no need to wait with initialization until constructor is called in this case, as everything is known in advance.

Now, you may hover direction$ field and see it's inferred type (I assume you are using vscode).