Question

private runMiddlewares(route: Route | ExceptionRoute, request: HttpRequest, response: HttpResponse): Promise<any> {
    return new Promise((resolve, reject) => {
        try {
            route.middlewares.forEach(async (middleware: IMiddleware) => {
                console.log('begin run middleware');
                await middleware.process(request, response);
                console.log('resolve run middleware');
                console.log(request.body);
            });
            console.log('resolve all runMiddlewares');
            resolve();
        } catch (e) {
            reject(e);
        }
    });
}

我已经编写了此函数runMiddlewares，当所有middleware.process()都已解析后，该函数理想情况下为resolve（）。我正在使用打字稿await功能，但似乎无法正常工作。我希望route.middlewares.forEach(

内会发生这种情况

“开始运行中间件”
然后等待解决
“解决运行中间件”

forEach循环中的所有中间件都将继续执行此操作，然后在列表全部完成后，才打印“ resolve all runMiddlewares”，最后private runMiddlewares( ... )应该被解决。

但是相反，forEach现在得到了立即解决，从而阻止了所有中间件的完成。

应如何处理？我认为await会在forEach循环内处理它，直到resolve中的runMiddlewares才会被调用。我在这里想念什么？

Answer 1

您可以使用map从中间件创建一个承诺数组。可以将此承诺数组传递给Promise.all，它会在解决数组的每个单个承诺时解决。

await Promise.all(route.middlewares.map((middleware: IMiddleware) => {
            console.log('begin run middleware');
            const promise = middleware.process(request, response);
            console.log('resolve run middleware');
            console.log(request.body);
            return promise
        });

或更紧凑：

runMiddlewares(...) {
  return Promise.all(
    route.middlewares.map((middleware: IMiddleware) => {
      return middleware.process(request, response))
    })
  )
}

Answer 2

因此，按照推荐（https://cn.eslint.org/docs/3.0.0/rules/no-await-in-loop），我将其编写如下

private runMiddlewares(route: Route | ExceptionRoute, request: HttpRequest, response: HttpResponse): Promise<any> {
    return new Promise(async (resolve, reject) => {
        try {
            const middlewarePromiseArry: any[] = [];
            route.middlewares.forEach((middleware: IMiddleware) => {
                console.log('begin run middleware');
                middlewarePromiseArry.push(middleware.process(request, response));
                // removed the use of await inside of forEach loop following this link: https://cn.eslint.org/docs/3.0.0/rules/no-await-in-loop
                // await middleware.process(request, response);
                // console.log('resolve run middleware');
                // console.log(request.body);
            });

            await Promise.all(middlewarePromiseArry);
            console.log('resolve all runMiddlewares');
            resolve();
        } catch (e) {
            reject(e);
        }
    });
}

我很高兴接受进一步的答案和建议/改进：）

Javascript Promise解决混乱

2 个答案: