4 ms·

You can fix async await with express by just installing a package.

by cypress66 2y ago

mbork_pl 2y ago
Which package?
- basil-rash 2y ago
  This one does it via monkey patching express internals to make the fix transparent: https://www.npmjs.com/package/express-async-errors https://www.npmjs.com/package/express-async-errors
  - hombre_fatal 2y ago
    That still doesn't address the main difference between Express and Koa. In Express, the route handlers send the response directly so your middleware can only be "beforeware". In Koa, the route handlers update a response object that bubbles back up the stack before it's sent, so you can write both beforeware and afterware (so, real middleware). For example: app.use(async (ctx, next) => { console.log('Request is going down', ctx.request.body) await next() console.log('Response is coming up', ctx.response.body) })
    - basil-rash 2y ago
      Sure, but that doesn’t seem very relevant to this thread. Also in express there are certainly ways to do what you say, for instance you could make a middleware like the following: app.use(async (req, res, next) => { console.log("Request is going down", req.body) await next() console.log("Response is coming up", res.data) res.send(res.data) }) app.get("/", function (req, res) { res.data = { content: "Hello World" } })
    - pcthrowaway 2y ago
      I don't think anyone was claiming Express and Koa were carbon copies of one another, only that Koa's benefits over Express are minor and Express is much more relevant. Your claim that "you have to catch your errors or your app can crash" can be addressed trivially. My Express is rusty and I didn't use exact types, but something like this would do: type ExpressMiddlewareNextOptional = (req: Record<any, any>, res: Record<any, any>, next?: (error: any) => void) => any; type ExpressMiddleware = (req: Record<any, any>, res: Record<any, any>, next: (error: any) => void) => any; const mid = (middleware: ExpressMiddlewareNextOptional): ExpressMiddleware => { return (req, res, next) => { const result = middleware(req, res, next); if (result instanceof Promise) { result.catch((err) => next(err)); } } } // example usage: app.get('somepath', mid(async (req, res) => { throw new Error('Oopsie!') })) I used Koa a long time ago before JS had promises and async/await, and it was a relief then, but since Promises the ergonomics of Express have been better (compared to Koa of 8-9 years ago, it's possible Koa is on par or better now). When I started a new project 4 years ago I saw that express had >100X the active usage of Koa, and many, many more packages and pre-built middleware. That's why I say Koa is largely not relevant. They're both very lightweight libraries, but the ecosystem for Express is much larger, and as mentioned, I've seen maybe 1 company using Koa in the last 5 years. I'm not saying not to use it, and I'm not saying it's not good, but OP was asking for a comparison to "competitors", and I think the ecosystem around a web framework is one of the most important considerations in choosing one. There are thousands of Node.js frameworks, and I'm sure there are many novel ideas among many excellent frameworks I've never even heard of, but the only ones I'd call "competitors" to Express are the ones operating in or near the same weight class. OP mentioned Fastify which is no more than 1 order magnitude away from express in market share, and Koa, which is at least 2 orders of magnitude below Express in active market share. My response was just pointing out that Koa is largely irrelevant when considering Node.js frameworks as "competition to Express". If they had asked about "alternatives" instead I probably wouldn't have mentioned it "not being a thing", but just pointed out that Express/Koa are spiritually very similar (as two ultra-minimalist frameworks created by TJ Hollowaychuk), but Express's ecosystem is so much larger that someone who isn't already familiar with Koa would very likely be better off choosing Express for anything serious.
      - 2y ago

You can fix async await with express by just installing a package.

mbork_pl 2y ago

Which package?

basil-rash 2y ago
This one does it via monkey patching express internals to make the fix transparent: https://www.npmjs.com/package/express-async-errors https://www.npmjs.com/package/express-async-errors
- hombre_fatal 2y ago
  That still doesn't address the main difference between Express and Koa. In Express, the route handlers send the response directly so your middleware can only be "beforeware". In Koa, the route handlers update a response object that bubbles back up the stack before it's sent, so you can write both beforeware and afterware (so, real middleware). For example: app.use(async (ctx, next) => { console.log('Request is going down', ctx.request.body) await next() console.log('Response is coming up', ctx.response.body) })
  - basil-rash 2y ago
    Sure, but that doesn’t seem very relevant to this thread. Also in express there are certainly ways to do what you say, for instance you could make a middleware like the following: app.use(async (req, res, next) => { console.log("Request is going down", req.body) await next() console.log("Response is coming up", res.data) res.send(res.data) }) app.get("/", function (req, res) { res.data = { content: "Hello World" } })
  - pcthrowaway 2y ago
    I don't think anyone was claiming Express and Koa were carbon copies of one another, only that Koa's benefits over Express are minor and Express is much more relevant. Your claim that "you have to catch your errors or your app can crash" can be addressed trivially. My Express is rusty and I didn't use exact types, but something like this would do: type ExpressMiddlewareNextOptional = (req: Record<any, any>, res: Record<any, any>, next?: (error: any) => void) => any; type ExpressMiddleware = (req: Record<any, any>, res: Record<any, any>, next: (error: any) => void) => any; const mid = (middleware: ExpressMiddlewareNextOptional): ExpressMiddleware => { return (req, res, next) => { const result = middleware(req, res, next); if (result instanceof Promise) { result.catch((err) => next(err)); } } } // example usage: app.get('somepath', mid(async (req, res) => { throw new Error('Oopsie!') })) I used Koa a long time ago before JS had promises and async/await, and it was a relief then, but since Promises the ergonomics of Express have been better (compared to Koa of 8-9 years ago, it's possible Koa is on par or better now). When I started a new project 4 years ago I saw that express had >100X the active usage of Koa, and many, many more packages and pre-built middleware. That's why I say Koa is largely not relevant. They're both very lightweight libraries, but the ecosystem for Express is much larger, and as mentioned, I've seen maybe 1 company using Koa in the last 5 years. I'm not saying not to use it, and I'm not saying it's not good, but OP was asking for a comparison to "competitors", and I think the ecosystem around a web framework is one of the most important considerations in choosing one. There are thousands of Node.js frameworks, and I'm sure there are many novel ideas among many excellent frameworks I've never even heard of, but the only ones I'd call "competitors" to Express are the ones operating in or near the same weight class. OP mentioned Fastify which is no more than 1 order magnitude away from express in market share, and Koa, which is at least 2 orders of magnitude below Express in active market share. My response was just pointing out that Koa is largely irrelevant when considering Node.js frameworks as "competition to Express". If they had asked about "alternatives" instead I probably wouldn't have mentioned it "not being a thing", but just pointed out that Express/Koa are spiritually very similar (as two ultra-minimalist frameworks created by TJ Hollowaychuk), but Express's ecosystem is so much larger that someone who isn't already familiar with Koa would very likely be better off choosing Express for anything serious.
    - 2y ago