TYPESCRIPT

literal types typescript

type Easing = "ease-in" | "ease-out" | "ease-in-out";
 
class UIElement {
  animate(dx: number, dy: number, easing: Easing) {
    if (easing === "ease-in") {
      // ...
    } else if (easing === "ease-out") {
    } else if (easing === "ease-in-out") {
    } else {
      // It's possible that someone could reach this
      // by ignoring your types though.
    }
  }
}
 
let button = new UIElement();
button.animate(0, 0, "ease-in");
button.animate(0, 0, "uneasy");
Argument of type '"uneasy"' is not assignable to parameter of type 'Easing'.
Argument of type '"uneasy"' is not assignable to parameter of type 'Easing'.
Try