Apply a function to the wrapped value if Ok and return a new Ok
containing the resulting value; or if it is Err return it
unmodified.
This differs from map in that thenFn returns another Result.
You can use andThen to combine two functions which both create a Result
from an unwrapped type.
You may find the .then method on an ES6 Promise helpful for comparison: if
you have a Promise, you can pass its then method a callback which returns
another Promise, and the result will not be a nested promise, but a single
Promise. The difference is that Promise#then unwraps all layers to only
ever return a single Promise value, whereas Result.andThen will not unwrap
nested Results.
Apply a function to the wrapped value if
Ok
and return a newOk
containing the resulting value; or if it isErr
return it unmodified.This differs from
map
in thatthenFn
returns anotherResult
. You can useandThen
to combine two functions which both create aResult
from an unwrapped type.You may find the
.then
method on an ES6Promise
helpful for comparison: if you have aPromise
, you can pass itsthen
method a callback which returns anotherPromise
, and the result will not be a nested promise, but a singlePromise
. The difference is thatPromise#then
unwraps all layers to only ever return a singlePromise
value, whereasResult.andThen
will not unwrap nestedResult
s.This is is sometimes also known as
bind
, but not aliased as such becausebind
already means something in JavaScript.Examples