typescript 打字稿承诺泛型类型
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Typescript promise generic type
提问by VJAI
I've a sample Promise function like below. On success I return a numberand on false I return string. The compiler is complaining to specify some kind of generic type to the promise. In this case what type I've to specify? Do I've to specify like Promise<number>or Promise<number | string>?
我有一个像下面这样的示例 Promise 函数。成功时返回 a number，失败时返回string。编译器抱怨为承诺指定某种泛型类型。在这种情况下，我必须指定什么类型？我必须指定 likePromise<number>或Promise<number | string>？
function test(arg: string): Promise {
return new Promise((resolve, reject) => {
if (arg === "a") {
resolve(1);
} else {
reject("1");
}
});
}
回答by Dave Templin
The generic type of the Promise should correspond to the non-error return-type of the function. The error is implicitly of type anyand is not specified in the Promise generic type.
Promise 的泛型类型应该对应于函数的非错误返回类型。该错误属于隐式类型any，未在 Promise 泛型类型中指定。
So for example:
例如：
function test(arg: string): Promise<number> {
return new Promise<number>((resolve, reject) => {
if (arg === "a") {
resolve(1);
} else {
reject("1");
}
});
}
