typescript

Question

如何实现下面的'createCounter'功能？

function createCounter(key: string) {
    return {[key]:0} // Note this doesn't work
}

const obj = createCounter('sum')
obj.sum += 20 // works
obj.prop = 0  // oops: no such property

谢谢

Answer 1

您可以通过为 key 参数指定泛型来实现。这是具有正确行为的代码：

function createCounter<K extends PropertyKey>(key: K): { [H in K]: Record<H, number> }[K] {
    return { [key]: 0 } as any; // a cast is sadly required because TS isn't smart enough
}

const obj = createCounter('sum')
obj.sum += 20 // works
obj.prop = 0  // oops: no such property

TypeScript Playground Link

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