unicorn/no-null Style

🛠️ An auto-fix is available for this rule for some violations.

What it does

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

Why is this bad?

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

Examples of incorrect code for this rule:

let foo = null;

Examples of correct code for this rule:

let foo;

Configuration

This rule accepts a configuration object with the following properties:

checkStrictEquality

type: boolean

default: false

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

How to use

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

CLI

oxlint --deny unicorn/no-null

Config (.oxlintrc.json)

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

References

• Rule Source