undoredo

Simple undo/redo functionality for Java(Type)Script

See online demo

jest example

``typescript
let hist = new Hist(1);
let count = 0;
hist.add({Redo: ()=>{count++}, Undo: ()=>{count--}})
expect(count).toBe(1);
expect(hist.UndoLength).toBe(1);
hist.undo();
expect(count).toBe(0);
expect(hist.RedoLength).toBe(1);
hist.redo();
expect(count).toBe(1);
``