打字稿承诺通用类型 [英] Typescript promise generic type

问题描述

我有一个示例Promise函数，如下所示.成功时，我返回number，如果失败，则返回string.编译器抱怨为promise指定某种通用类型.在这种情况下，我必须指定哪种类型?我必须指定Promise<number>还是Promise<number | string>吗?

I've a sample Promise function like below. On success I return a number and 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>?

function test(arg: string): Promise {
    return new Promise((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}

推荐答案

Promise的通用类型应对应于该函数的非错误返回类型.该错误隐式为any类型，并且未在Promise泛型类型中指定.

The generic type of the Promise should correspond to the non-error return-type of the function. The error is implicitly of type any and is not specified in the Promise generic type.

例如:

function test(arg: string): Promise<number> {
    return new Promise<number>((resolve, reject) => {
        if (arg === "a") {
            resolve(1);
        } else {
            reject("1");
        }
    });
}

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