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eslint-plugin-promise
Advanced tools
The eslint-plugin-promise package is an ESLint plugin that enforces best practices and common idioms for dealing with promises in JavaScript. It provides a set of rules that catch common mistakes and enforce conventions when working with promises.
Avoiding creation of new promises outside of utility libraries
This rule ensures that the executor function of a new Promise has the parameters named 'resolve' and 'reject'.
/* eslint promise/param-names: 'error' */
new Promise((resolve, reject) => { /* executor function */ });
Ensuring that each time a then() is applied to a promise, a catch() is applied as well
This rule enforces the use of catch() on unhandled promises.
/* eslint promise/catch-or-return: 'error' */
promise.then(function(data) {
// handle data
}).catch(function(error) {
// handle error
});
Enforcing the return of a promise in certain contexts
This rule ensures that promise chains always return a value, preventing silent failures and unhandled rejections.
/* eslint promise/always-return: 'error' */
function foo() {
return doSomething().then(function() {
// do something else
return 'result';
});
}
This plugin provides ESLint rules for async/await syntax, which is related to promises. It helps to enforce best practices and catch common mistakes when using async/await, but it does not focus on promises directly.
Part of the 'eslint-plugin-standard' plugin includes rules that are applicable to promises, as it adheres to the JavaScript Standard Style. However, it covers a broader range of JavaScript features and is not solely focused on promises.
Enforce best practices for JavaScript promises.
You'll first need to install ESLint:
npm install eslint --save-dev
Next, install eslint-plugin-promise
:
npm install eslint-plugin-promise --save-dev
Note: If you installed ESLint globally (using the -g
flag) then you must
also install eslint-plugin-promise
globally.
Add promise
to the plugins section of your .eslintrc.json
configuration
file. You can omit the eslint-plugin-
prefix:
{
"plugins": ["promise"]
}
Then configure the rules you want to use under the rules section.
{
"rules": {
"promise/always-return": "error",
"promise/no-return-wrap": "error",
"promise/param-names": "error",
"promise/catch-or-return": "error",
"promise/no-native": "off",
"promise/no-nesting": "warn",
"promise/no-promise-in-callback": "warn",
"promise/no-callback-in-promise": "warn",
"promise/avoid-new": "warn",
"promise/no-new-statics": "error",
"promise/no-return-in-finally": "warn",
"promise/valid-params": "warn",
"promise/no-multiple-resolved": "error"
}
}
or start with the recommended rule set:
eslint.config.js
:
import pluginPromise from 'eslint-plugin-promise'
export default [
// ...
pluginPromise.configs['flat/recommended'],
]
.eslintrc.*
:
{
"extends": ["plugin:promise/recommended"]
}
💼 Configurations enabled in.
⚠️ Configurations set to warn in.
🚫 Configurations disabled in.
✅ Set in the flat/recommended
configuration.
✅ Set in the recommended
configuration.
🔧 Automatically fixable by the --fix
CLI option.
Name | Description | 💼 | ⚠️ | 🚫 | 🔧 |
---|---|---|---|---|---|
always-return | Require returning inside each then() to create readable and reusable Promise chains. | ✅ | |||
avoid-new | Disallow creating new promises outside of utility libs (use pify instead). | ✅ | |||
catch-or-return | Enforce the use of catch() on un-returned promises. | ✅ | |||
no-callback-in-promise | Disallow calling cb() inside of a then() (use nodeify instead). | ✅ | |||
no-multiple-resolved | Disallow creating new promises with paths that resolve multiple times. | ||||
no-native | Require creating a Promise constructor before using it in an ES5 environment. | ✅ | |||
no-nesting | Disallow nested then() or catch() statements. | ✅ | |||
no-new-statics | Disallow calling new on a Promise static method. | ✅ | 🔧 | ||
no-promise-in-callback | Disallow using promises inside of callbacks. | ✅ | |||
no-return-in-finally | Disallow return statements in finally() . | ✅ | |||
no-return-wrap | Disallow wrapping values in Promise.resolve or Promise.reject when not needed. | ✅ | |||
param-names | Enforce consistent param names and ordering when creating new promises. | ✅ | |||
prefer-await-to-callbacks | Prefer async /await to the callback pattern. | ||||
prefer-await-to-then | Prefer await to then() /catch() /finally() for reading Promise values. | ||||
valid-params | Enforces the proper number of arguments are passed to Promise functions. | ✅ |
FAQs
Enforce best practices for JavaScript promises
We found that eslint-plugin-promise demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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