promise/prefer-await-to-callbacks

With callbacks, every step has to check err by hand and pass it on. A forgotten check drops the error, and try/catch around the call doesn't catch anything that happens later. With await, errors are thrown and the steps read from top to bottom.

The rule goes by names. It reports:

• a call to a function named callback or cb
• a function with a last parameter named callback or cb
• a function passed as the last argument, if its first parameter is named err or error

The last case has exceptions: event listeners (on, once, addEventListener, removeEventListener), the array methods map, every, forEach, some, find and filter, and calls inside an await or yield expression.

Configure

Off by default. To turn it on:

[lint.rules]
"promise/prefer-await-to-callbacks" = "error" # or "warn"

Examples

Reported:

function readConfig(path, callback) {
  fs.readFile(path, "utf8", (err, text) => {
    if (err) return callback(err);
    callback(null, JSON.parse(text));
  });
}

Not reported:

import { readFile } from "node:fs/promises";

async function readConfig(path) {
  const text = await readFile(path, "utf8");
  return JSON.parse(text);
}

server.on("error", err => console.error(err));
failures.forEach(err => console.error(err));
await retry(upload, err => err.code === "ETIMEDOUT");

When not to use it

Leave it off in code that has to offer or use a callback API, such as Express middleware or older Node.js libraries.