Docs / API / Js / Null

Null

Provides functionality for dealing with the Js.null<'a> type

t

RESCRIPT
type t<'a> = Js.null<'a> = Value('a) | Null

Local alias for Js.null<'a>

return

RESCRIPT
let return: 'a => t<'a>

Constructs a value of Js.null<'a> containing a value of 'a.

test

Deprecated

Use = Js.null directly

RESCRIPT
let test: t<'a> => bool

Returns true if the given value is empty (null), false otherwise.

empty

RESCRIPT
let empty: t<'a>

The empty value, null

getUnsafe

RESCRIPT
let getUnsafe: t<'a> => 'a

getExn

RESCRIPT
let getExn: t<'a> => 'a

bind

RESCRIPT
let bind: (t<'a>, 'a => 'b) => t<'b>

Maps the contained value using the given function.

If Js.null<'a> contains a value, that value is unwrapped, mapped to a 'b using the given function 'a => 'b, then wrapped back up and returned as Js.null<'b>.

Examples

RESCRIPT
let maybeGreetWorld = (maybeGreeting: Js.null<string>) =>
  Js.Null.bind(maybeGreeting, (. greeting) => greeting ++ " world!")

iter

RESCRIPT
let iter: (t<'a>, 'a => unit) => unit

Iterates over the contained value with the given function. If Js.null<'a> contains a value, that value is unwrapped and applied to the given function.

Examples

RESCRIPT
let maybeSay = (maybeMessage: Js.null<string>) =>
  Js.Null.iter(maybeMessage, (. message) => Js.log(message))

fromOption

RESCRIPT
let fromOption: option<'a> => t<'a>

Maps option<'a> to Js.null<'a>. Some(a) => a None => empty

from_opt

Deprecated

Use fromOption instead

RESCRIPT
let from_opt: option<'a> => t<'a>

toOption

RESCRIPT
let toOption: t<'a> => option<'a>

Maps Js.null<'a> to option<'a>. a => Some(a) empty => None

to_opt

Deprecated

Use toOption instead

RESCRIPT
let to_opt: t<'a> => option<'a>