Javascript 如何在typescript中键入承诺的回调?
我可以为键入回调。然后在我的承诺中,目前我暂时使用Javascript 如何在typescript中键入承诺的回调?,javascript,node.js,typescript,Javascript,Node.js,Typescript,我可以为键入回调。然后在我的承诺中,目前我暂时使用任何我想使用的字符串或类似的位 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(
任何我想使用的字符串或类似的位
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");
});
我收到的错误信息:
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'.
});
类型为“(hash:string)=>void”的参数不能分配给类型为“(value:{})=>void | PromiseLike”的参数。
参数“哈希”和“值”的类型不兼容。
类型“{}”不可分配给类型“string”。
});
考虑直接指定退货承诺类型新承诺
:
要么为Promise提供泛型类型参数,要么为md5
方法提供返回类型,要么两者都提供:
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")));
});
export const md5=(路径:string):Promise=>
新承诺((解决、拒绝)=>{
const hash=createHash(“sha1”);
const rs=createReadStream(路径);
rs.on(“错误”,拒绝);
rs.on(“数据”,chunk=>hash.update(chunk));
rs.on(“end”,()=>resolve(hash.digest(“hex”));
});
您所缺少的只是“返回”。更改为:
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")));
});
尝试使用新承诺(…
。这是一个匿名箭头函数。它不需要返回语句,除非函数体包装在{}中,否则无效。此代码将导致'{'预期的
错误
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")));
});
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")));
});