Js_undefined

Provides functionality for dealing with the Js.undefined('a) type

t

Local alias for Js.undefined('a)

type t<'a> = Js.undefined<'a>

return

Constructs a value of Js.undefined('a) containing a value of 'a.

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

test

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

let test: t<'a> => bool

testAny

Returns true if the given value is empty (undefined).

since 1.6.1

let testAny: 'a => bool

empty

The empty value, undefined

let empty: t<'a>

getUnsafe

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

getExn

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

bind

Maps the contained value using the given function. If Js.undefined('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.undefined('b).

RES
let maybeGreetWorld = (maybeGreeting: Js.undefined<string>) =>
  Js.Undefined.bind(maybeGreeting, (. greeting) => greeting ++ " world!")

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

iter

Iterates over the contained value with the given function. If Js.undefined('a) contains a value, that value is unwrapped and applied to the given function.

RES
let maybeSay = (maybeMessage: Js.undefined<string>) =>
  Js.Undefined.iter(maybeMessage, (. message) => Js.log(message))

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

fromOption

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

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

from_opt

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

toOption

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

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

to_opt

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