avoid-new.md

Disallow creating new promises outside of utility libs (use util.promisify instead) (promise/avoid-new)

🚫 This rule is disabled in the following configs: ✅ flat/recommended, ✅ recommended.

Avoid using new Promise in favour of utility libraries or Promise.resolve/reject.

Rule Details

Creating promises using new Promise can be used to promisify Node-style callbacks. However, you can use Node's util.promisify instead.

new Promise is also sometimes misused to wrap a value or error into a promise. However, this can be done more concisely and clearly with Promise.resolve and Promise.reject.

Examples of incorrect code for this rule:

function promisifiedFn(arg) {
  return new Promise((resolve, reject) => {
    callbackStyleFn(arg, (error, result) =>
      error ? reject(error) : resolve(result),
    )
  })
}

new Promise((resolve, reject) => resolve(1))
new Promise((resolve, reject) => reject(new Error('oops')))

Examples of correct code for this rule:

import util from 'util'
const promisifiedFn = util.promisify(callbackStyleFn)

Promise.resolve(1)
Promise.reject(new Error('oops'))

When Not To Use It

If you are creating a utility library without util.promisify or do not want to be notified when using new Promise, you can safely disable this rule.