Variable isNone`Const`

isNone: (fa: Option<unknown>) => fa is None

Returns true if the option is None, false otherwise.

Type Declaration

- (fa: Option<unknown>): fa is None
- Parameters
  - fa: Option<unknown>
  Returns fa is None

Example

import { some, none, isNone } from 'fp-ts/Option'

assert.strictEqual(isNone(some(1)), false)
assert.strictEqual(isNone(none), true)

Since

2.0.0