rx-undoable
Easily undo and redo RxJS observables.
Great for adding undo and redo buttons to Cycle.js applications.
Installation
npm install --save rx-undoable
Usage
; const numbers$ = RxObservable; const undo$ = RxObservable; // observable of undo intent, like clicking an undo button const undoableSum$ = ;
API
undoableScan(stream$, f, initialValue, undo$, [redo$, {historySize: Infinite}])
Which is equivalent to stream$.scan(f, initialValue)
, except that data is returned in this format:
past: ... present: thing future: ...
So to get the present data, use undoableScan(...).pluck('present')
.
Arguments:
stream$
: An RxJS stream
f
: A function as you would use with scan
or reduce
. (previousValue, currentValue) => nextValue
initialValue
: The initial value to be used as present
.
undo$
: An RxJS stream that will cause an undo each time it emits
redo$
: An optional RxJS stream that will cause a redo each time it emits
options
: An optional object carrying additional options
historySize
: A size limit for the past
array. Defaults to Infinity
Example
Let's take a simple counter example from the Cycle.js docs and add undo and redo buttons.
Before:
;;; { let action$ = RxObservable; let count$ = action$ ; return DOM: count$ ;} ;
After:
;;;; { let action$ = RxObservable; let undo$ = DOM; // NEW let redo$ = DOM; // NEW let count$ = ; // NEW return DOM: count$ ;} ;
Prior art
rx-undoable
was inspired by omnidan/redux-undo and the algorithm used is described very eloquently by Dan Abramov in the Redux documentation.
Contributing
Issues, pull requests and feedback of all sorts welcome! If you're unsure, send me an email at ncwjohnstone@gmail.com.