Created
February 6, 2020 05:27
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Fancy Express error handling
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| const app = require('express')(); | |
| const fs = require('fs'); | |
| // Resolves with a list of the filenames in dir, or rejects if dir doesn't exist or if something else goes wrong. | |
| function readFileNames(dir) { | |
| return new Promise((resolve, reject) => { | |
| fs.readdir(dir, (err, files) => { | |
| if (err) { | |
| reject(err); | |
| } else { | |
| resolve(files); | |
| } | |
| }); | |
| }); | |
| } | |
| // Returns a new async handler that is like the given one, but with promise rejections passed through to Express's "next" function. | |
| function forwardErrors(handler) { | |
| return (req, res, next) => handler(req, res).catch(next); | |
| } | |
| app.get('/', forwardErrors(async (req, res) => { | |
| if (req.query.dir == null) { | |
| throw new Error("A 'dir' query parameter must be provided."); | |
| } | |
| const results = await readFileNames(req.query.dir); | |
| res.status(200).send(`Files in ${req.query.dir}:\n${results.join("\n")}`); | |
| })); | |
| app.use(function(error, req, res, next) { | |
| res.status(500).send(error.toString()); | |
| }); | |
| app.listen(3000); | |
| /* Example output: | |
| sollux:express-error-test$ curl localhost:3000 | |
| Error: A 'dir' query parameter must be provided. | |
| sollux:express-error-test$ curl localhost:3000?dir=foo | |
| Error: ENOENT: no such file or directory, scandir 'foo' | |
| sollux:express-error-test$ curl localhost:3000?dir=. | |
| Files in .: | |
| index.js | |
| node_modules | |
| package-lock.json | |
| package.json | |
| */ |
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