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# simple-undo
[](https://travis-ci.org/mattjmattj/simple-undo)
simple-undo is a very basic javascript undo/redo stack for managing histories of basically anything.
Initially created to help fixing an issue in [drawingboard.js](https://github.com/Leimi/drawingboard.js/issues/29).
## Installation
### Bower
`bower install simple-undo`.
### NPM
`npm install simple-undo`
## Usage
If you are using simple-undo in the browser, a SimpleUndo object is exported in `window` after including simple-undo in your page, so it is very easy to use.
If you are using simple-undo as a nodejs module, just do `var SimpleUndo = require('simple-undo');`
```javascript
var myObject = {};
function myObjectSerializer(done) {
done(JSON.stringify(myObject));
}
function myObjectUnserializer(serialized) {
myObject = JSON.parse(serialized);
}
var history = new SimpleUndo({
maxLength: 10,
provider: myObjectSerializer
});
myObject.foo = 'bar';
history.save();
myObject.foo = 'baz';
history.save();
history.undo(myObjectUnserializer);
// myObject.foo == 'bar'
history.redo(myObjectUnserializer);
// myObject.foo == 'baz'
```
Another example is available on the [GitHub page of the project](http://mattjmattj.github.io/simple-undo/)
## Options and API
Accepted options are
* `provider` : required. a function to call on `save`, which should provide the current state of the historized object through the given `done` callback
* `maxLength` : the maximum number of items in history
* `opUpdate` : a function to call to notify of changes in history. Will be called on `save`, `undo`, `redo` and `clear`
SimpleUndo
* `initialize (initialState)` : registers the initial state of the managed object. If not call the default initial state is NULL
* `save ()` : calls the `provider` and registers whatever it gives
* `undo (callback)` : calls the callback with the previous state of the managed object in history
* `redo (callback)` : calls the callback with the next state of the managed object in history
* `clear ()` : clears the whole history, except the inital state if any
* `count ()` : returns the count of elements in history, apart from the inital state
## License
simple-undo is licensed under the terms of the [Beerware license](LICENSE).
2014 - Matthias Jouan
Generated by GNU Enscript 1.6.5.90.