Util.promisify
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Slides about new Node.js 8's util.promisify() feature
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Util.promisify
- 1. ✨ Node.js 8 ✨ util.promisify(original) Fran Herrero @leynar github.com/franher Node.js Barcelona 20 June 2017
- 2. It converts a callback-based function to a Promise-based one✅ standard callbacks functions (err, value) => …
- 3. 🚫non-standard callbacks functions (err, value1, value2, …) => … • child_process.exec • child_process.exec File • dns.lookup • dns.lookupService • fs.read • fs.write
- 4. 👩🎨Custom promisified functions 🎨 Symbol util.promisify.custom to override the return value of util.promisify()
- 5. But bluebird is still faster...🏎🏇 • During Node.js 8 lifecycle V8 JS engine will be updated to v6 • Right now shipped with V8 JS engine v5.8 • Keep your code third dependency agnostic. Use core built-in features!
Editor's Notes
- twitter poll I promise I’m gonna be short, then we’ll go to the pub to catch some beers
- If you want use an async/await function you should use follow example. Everybody know we should work and use standards callback function (err, value) => … What happen if we don’t have standard-callback functions?
- * If you promisify one of these functions, it returns an object of values (not a single value). promisify() handles non-standard callbacks via the internal symbol internal/util/customPromisifyArgs https://gist.github.com/franher/11411171213d0537ef48fc0bc6d07bd2
- This can be useful for cases where the original function does not follow the standard format of taking an error-first callback as the last argument. two standard functions have promisified versions due are not error first callback as last arguments but as first node 8.1.0 landed in https://github.com/nodejs/node/pull/13316/files fs.exists not error-first callback (boolean parameter) https://gist.github.com/franher/0680a03ae151e8df278c92699f47b92c
- since V8 v5.7 a lot of improvements on perfomance Node 8 was shipped with V8 v5.8 https://kyrylkov.com/2017/04/25/native-promises-async-functions-nodejs-8-performance/
- since V8 v5.7 a lot of improvements on perfomance Node 8 was shipped with V8 v5.8 https://kyrylkov.com/2017/04/25/native-promises-async-functions-nodejs-8-performance/