unicorn/no-null | Bun Docs

JavaScript has two values for "nothing". If you only use undefined, you need one check instead of two. Default parameters and destructuring defaults also apply to undefined but not to null.

Strict comparisons such as x === null are allowed by default, because you often need to check what an API returned.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"unicorn/no-null" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"unicorn/no-null" = ["error", {
  checkStrictEquality = false,
  checkArguments = true,
}]

Examples#

example.js1 problem

let selected = null;

example.jsNo problems

let selected;

if (document.querySelector("dialog") === null) {
  selected = undefined;
}

Options#

Option	Default	What it does
`checkStrictEquality`	`false`	Also report `x === null` and `x !== null`.
`checkArguments`	`true`	Report `null` that's passed to a function or a constructor.

example.jswith { "checkStrictEquality": true }1 problem

if (selected === null) {
  selected = first();
}

example.jswith { "checkArguments": false }No problems

save(user, null);

When not to use it#

Many APIs return or expect null, like the DOM, JSON and databases. If your code talks to them a lot, this rule gets in the way.