Undefined
Provides functionality for dealing with the Js.undefined<'a>
type
t
type t<'a> = Js.undefined<'a>
Local alias for Js.undefined<'a>
return
let return: 'a => t<'a>
Constructs a value of Js.undefined<'a>
containing a value of 'a
.
test
Deprecated
Use = Js.undefined directly
let test: t<'a> => bool
Returns true
if the given value is empty (undefined), false
otherwise.
testAny
let testAny: 'a => bool
Returns true
if the given value is empty (undefined).
since 1.6.1
empty
let empty: t<'a>
The empty value, undefined
getUnsafe
let getUnsafe: t<'a> => 'a
getExn
let getExn: t<'a> => 'a
bind
let bind: (t<'a>, 'a => 'b) => t<'b>
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>
.
Examples
RESCRIPTlet maybeGreetWorld = (maybeGreeting: Js.undefined<string>) =>
Js.Undefined.bind(maybeGreeting, (. greeting) => greeting ++ " world!")
iter
let iter: (t<'a>, 'a => unit) => unit
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.
Examples
RESCRIPTlet maybeSay = (maybeMessage: Js.undefined<string>) =>
Js.Undefined.iter(maybeMessage, (. message) => Js.log(message))
fromOption
let fromOption: option<'a> => t<'a>
Maps option<'a>
to Js.undefined<'a>
.
Some(a)
=> a
None
=> empty
from_opt
Deprecated
Use fromOption instead
let from_opt: option<'a> => t<'a>
toOption
let toOption: t<'a> => option<'a>
Maps Js.undefined<'a>
to option<'a>
a
=> Some(a)
empty
=> None
to_opt
Deprecated
use toOption instead
let to_opt: t<'a> => option<'a>