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Easy undo-redo in JavaScript.
function UndoItem (perform, data) {
this.perform = perform;
this.data = data;
}
/**
* UndoStack:
* Easy undo-redo in JavaScript.
**/
function UndoStack(self) {
this.stack = [];
this.current = -1;
this.self = self;
}
/**
* UndoStack#push (action, data);
* perform(true, data) -> Function which performs redo based on previous state
* perform(false, data) -> Function which performs undo based on current state
* data -> Argument passed to undo/redo functions
**/
UndoStack.prototype.push = function (perform, data) {
this.current++;
// We need to invalidate all undo items after this new one
// or people are going to be very confused.
this.stack.splice(this.current);
this.stack.push(new UndoItem(perform, data));
};
UndoStack.prototype.undo = function () {
var item;
if (this.current >= 0) {
item = this.stack[this.current];
item.perform.call(this.self, false, item.data);
this.current--;
} else {
throw new Error("Already at oldest change");
}
};
UndoStack.prototype.redo = function () {
var item;
item = this.stack[this.current + 1];
if (item) {
item.perform.call(this.self, true, item.data);
this.current++;
} else {
throw new Error("Already at newest change");
}
};
UndoStack.prototype.invalidateAll = function () {
this.stack = [];
this.current = -1;
};
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