Function isNullish

Checks if a value is null or undefined.

Example

Basic usage

isNullish(null) // true
isNullish(undefined) // true
isNullish(0) // false
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Type narrowing

const value: string | null | undefined

if (isNullish(value)) {
  value // type: null | undefined
} else {
  value // type: string
}

// or
if (!isNullish(value)) {
  value // type: string
} else {
  value // type: null | undefined
}
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Paired with assert

import { assert } from 'uft'

const token: string | null | undefined
assert(!isNullish(token), 'received nullish token')
token // string
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