Undefined
Provide utilities around Js.undefined
.
t
REStype t<'a> = Js.undefined<'a>
Local alias for 'a Js.undefined.
return
RESlet return: 'a => t<'a>
Constructs a value of Js.undefined<'a>
containing a value of 'a
.
test
RESlet test: t<'a> => bool
Returns true
if the given value is empty (undefined), false
otherwise.
testAny
RESlet testAny: 'a => bool
Since 1.6.1 Returns true
if the given value is empty (undefined).
empty
RESlet empty: t<'a>
The empty value, undefined
.
getUnsafe
RESlet getUnsafe: t<'a> => 'a
getExn
RESlet getExn: t<'a> => 'a
bind
RESlet 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>
.
RESlet maybeGreetWorld = (maybeGreeting: Js.undefined<string>) =>
Js.Undefined.bind(maybeGreeting, (. greeting) => greeting ++ " world!")
iter
RESlet 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.
RESlet maybeSay = (maybeMessage: Js.undefined<string>) =>
Js.Undefined.iter(maybeMessage, (. message) => Js.log(message))
fromOption
RESlet fromOption: option<'a> => t<'a>
Maps option<'a>
to Js.undefined<'a>
.
Some(a)
=> a
None
=> empty
from_opt
RESlet from_opt: option<'a> => t<'a>
toOption
RESlet toOption: t<'a> => option<'a>
Maps Js.undefined<'a>
to option<'a>
a
=> Some(a)
empty
=> None
to_opt
RESlet to_opt: t<'a> => option<'a>