Callback Patterns and Error-First Convention

[giscus[bot]]

Callback Patterns and Error-First Convention

Error-first callbacks, sync vs async invocation, callback hell, and how Node's core APIs enforce the convention.

https://www.thenodebook.com/async-patterns/callback-patterns

[tomek278]

Hi, I have question about this statement:
"But if you've ever logged this inside a readFile callback using a regular function and seen an unfamiliar object with fd, buffers, and encoding properties, that's the ReadFileContext"

For me this logs undefined instead of ReadFileContext object - is it dependent on version of node or something else? Or I'm missing something? I'm running Node v24.11.1 on Windows

import fs from "fs";
fs.readFile("./file.txt", function (err, data) {
if (err) throw err;
console.log("this", this);
});