The fs module includes promisified methods since Node 11 (#tilPost)

That’s a quick one. πŸ™ˆ
When writing Node.js scripts that use the fs module, I usually used the util.promisify method to promisify the file-system methods. Promises-based metheds allow using async/await that makes code easier to grasp…

That's a quick one. πŸ™ˆ

When writing Node.js scripts that use the fs module, I usually used the util.promisify method to promisify the file-system methods. Promises-based metheds allow using async/await that makes code easier to grasp.

Today I learned that since Node.js 11 the fs module provides "promisified" methods in a promises property. πŸŽ‰

// old way have using promise-based fs methods
const { readFile } = require("fs");
const { promisify } = require('util');
const promisifiedReadFile = promisify(readFile);

promisifiedReadFile(__filename, { encoding: "utf8" })
  .then(data => console.log(data));

// --------------------

// new way of using promise-based fs methods
// no util.promisify!!!
const { readFile } = require("fs").promises;
readFile(__filename, { encoding: "utf8" })
  .then(data => console.log(data));

Using the promises property you can now skip the step to transform callbacks into promises and there is no need to use promisify. That's excellent news to flatten some source code and go all in with async/await!

fs/promises is available since Node.js 14

Section titled `fs/promises` is available since Node.js 14

Update: Since Node.js 14 the fs module provides two ways to use the promises-based file-system methods. The promisified methods are available via require('fs').promises or require('fs/promises').

// Since Node.js v14: use promise-based fs methods
// no util.promisify!!!
const { readFile } = require("fs/promises");
readFile(__filename, { encoding: "utf8" })
  .then(data => console.log(data));

I'm very excited about the /promises path addition. The Node.js maintainers seemed to agree on this way to expose more promise-based methods of existing modules in the future.

In Node.js v15 the Timers module also provides an experimental timers/promises package. That means you can do await setTimeout soon – Node.js is evolving and that means less util.promisify and more coding! πŸŽ‰

If you want to read more Node.js tips and tricks head over to the Node.js section on my blog or subscribe to my newsletter below.


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