Question

我可以在诺言中键入.then的回调，目前我暂时使用any位，我想使用string或类似名称。

有人知道如何键入我的函数md5吗？

export const md5 = (path: string) =>
  new Promise((resolve, reject) => {
    const hash = createHash("sha1");
    const rs = createReadStream(path);
    rs.on("error", reject);
    rs.on("data", chunk => hash.update(chunk));
    rs.on("end", () => resolve(hash.digest("hex")));
  });


  it("should hash md5 a file", () => {
    // error here on hash:string, if I use instead any it works
    const m = md5(fileName).then((hash: string) => {
      assert.strictEqual(m, "4738e449ab0ae7c25505aab6e88750da");
    });

我收到的错误：

Argument of type '(hash: string) => void' is not assignable to parameter of type '(value: {}) => void | PromiseLike<void>'.
  Types of parameters 'hash' and 'value' are incompatible.
    Type '{}' is not assignable to type 'string'.
  });

Answer 1

考虑直接指定返回的Promise类型new Promise<string>：

export const md5 = (path: string) =>
  new Promise<string>((resolve, reject) => {
    const hash = createHash("sha1");
    const rs = createReadStream(path);
    rs.on("error", reject);
    rs.on("data", chunk => hash.update(chunk));
    rs.on("end", () => resolve(hash.digest("hex")));
  });

还请检查测试中是否有错误，将m替换为hash：

assert.strictEqual(hash, "4738e449ab0ae7c25505aab6e88750da");

Answer 2

或者给Promise一个泛型类型参数，或者给你的md5方法一个返回类型，或者两者都做：

export const md5 = (path: string): Promise<string> =>
  new Promise<string>((resolve, reject) => {
    const hash = createHash("sha1");
    const rs = createReadStream(path);
    rs.on("error", reject);
    rs.on("data", chunk => hash.update(chunk));
    rs.on("end", () => resolve(hash.digest("hex")));
  });

Answer 3

您所缺少的只是“返回”。更改为此：

export const md5 = (path: string) =>
    return new Promise((resolve, reject) => {
        const hash = createHash("sha1");
        const rs = createReadStream(path);
        rs.on("error", reject);
        rs.on("data", chunk => hash.update(chunk));
        rs.on("end", () => resolve(hash.digest("hex")));
    });

如何在打字稿中键入诺言的回调？

3 个答案: