unicorn/no-null Style

⚠️ 🛠️ A dangerous auto-fix is available for this rule for some violations.

Disallow the use of the null literal, to encourage using undefined instead.

There are some reasons for using undefined instead of null.

From experience, most developers use null and undefined inconsistently and interchangeably, and few know when to use which.
Supporting both null and undefined complicates input validation.
Using null makes TypeScript types more verbose: type A = {foo?: string | null} vs type A = {foo?: string}.

Examples of incorrect code for this rule:

javascript

let foo = null;

Examples of correct code for this rule:

javascript

let foo;

Configuration

This rule accepts a configuration object with the following properties:

type: boolean

default: true

When set to true, disallow the use of null as a direct function call or constructor argument.

type: boolean

default: false

When set to true, the rule will also check strict equality/inequality comparisons (=== and !==) against null.

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)Config (oxlint.config.ts)CLI

json

{
  "rules": {
    "unicorn/no-null": "error"
  }
}

import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "unicorn/no-null": "error",
  },
});

bash

oxlint --deny unicorn/no-null

This rule was added in v0.0.21.