unicorn/no-typeof-undefined Pedantic
What it does
Disallow typeof comparisons with undefined.
Why is this bad?
Checking if a value is undefined by using typeof value === 'undefined' is needlessly verbose. It's generally better to compare against undefined directly. The only time typeof is needed is when a global variable potentially does not exists, in which case, using globalThis.value === undefined may be better.
Examples
Examples of incorrect code for this rule:
javascript
typeof foo === 'undefined';Examples of correct code for this rule:
javascript
foo === undefined;Configuration
This rule accepts a configuration object with the following properties:
checkGlobalVariables
type: boolean
default: false
If set to true, also report typeof x === "undefined" when x may be a global variable that is not declared (commonly checked via typeof foo === "undefined").
How to use
To enable this rule using the config file or in the CLI, you can use:
json
{
"rules": {
"unicorn/no-typeof-undefined": "error"
}
}bash
oxlint --deny unicorn/no-typeof-undefined