Function isNull

Checks if a value is null.

Example

Basic usage

isNull(null) // true
isNull(undefined) // false
isNull(0) // false
Copy

Type narrowing

const value: string | null

if (isNull(value)) {
  value // type: null
} else {
  value // type: string
}

// or
if (!isNull(value)) {
  value // type: string
} else {
  value // type: null
}
Copy

Paired with assert

import { assert, isNull } from 'uft'

const token: string | null
assert(!isNull(token), 'received null token')
token // type: string
Copy