@algosail/nil

Utilities for working with nullable values (null | undefined). A thin alternative to Maybe for code that deals directly with nullable primitives.

Contents

• nil
• init
• isNil / isNotNil
• fromPredicate
• fromMaybe

nil

nil :: a -> Nil a

Returns the value if it is non-nil, otherwise returns null.

nil(42) // => 42
nil('hello') // => 'hello'
nil(0) // => 0          — 0 is not nil
nil(null) // => null
nil(undefined) // => null

init

init :: () -> Nil never

Returns the empty nil value (null). Useful as a typed zero/mempty.

init() // => null

isNil / isNotNil

isNil    :: Nil a -> Boolean
isNotNil :: Nil a -> Boolean

Check whether a value is nil (null or undefined).

isNil(null) // => true
isNil(undefined) // => true
isNil(0) // => false
isNil('') // => false
isNil(false) // => false

isNotNil(42) // => true
isNotNil(null) // => false

fromPredicate

fromPredicate :: (a -> Boolean) -> Nil a -> Nil a

Returns the value if it is non-nil and satisfies the predicate; otherwise null.

fromPredicate((x) => x > 0)(5) // => 5
fromPredicate((x) => x > 0)(-1) // => null
fromPredicate((x) => x > 0)(null) // => null

fromMaybe

fromMaybe :: Maybe a -> Nil a

Converts a Maybe to a nullable value — Nothing becomes null, Just(a) becomes a.

fromMaybe(just(42)) // => 42
fromMaybe(nothing()) // => null
fromMaybe(just(null)) // => null  — the wrapped value