TypeScript singleton types All In One

单例类型 / 字面量类型

singleton types / literal types

1. enum member types

2. numeric literal types

3. string literal types

type EventName = 'click' | 'scroll' | 'mousemove';

function handleEvent(ele: Element, event: EventName) {
    // do something
}

handleEvent(document.getElementById('btn') as HTMLElement, 'scroll');
// ✅
handleEvent(document.getElementById('btn') as HTMLElement, 'dblclick');
// ❌ Argument of type '"dblclick"' is not assignable to parameter of type 'EventName'.(2345)

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From： https://www.cnblogs.com/xgqfrms/p/17129918.html