Fall2020.Day16.CommandObjects/index.html at master · CS3550/Fall2020.Day16.CommandObjects · GitHub

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<!DOCTYPE html>
<html>
<head>
    <meta charset='utf-8'>
    <meta http-equiv='X-UA-Compatible' content='IE=edge'>
    <title>Page Title</title>
    <meta name='viewport' content='width=device-width, initial-scale=1'>

</head>
<body>
    <button onclick="doIncrement()">Increment</button>
    <button onclick="doDecrement()">Decrement</button>
    <button onclick="undo()">Undo</button>
    <button onclick="redo()">Redo</button>
    <script>
        class Model{
            constructor(){
                this.value = 0;
            }
            increment(){
                this.value++;
                console.log(this.value);
            }
            decrement(){
                this.value--;
                console.log(this.value);
            }
        }

        let model = new Model();

        let undoStack = [];
        let redoStack = [];

        class IncrementCommand{
            constructor(model){
                this.model = model;
            }
            do(){
                this.model.increment();
            }
            undo(){
                this.model.decrement()
            }
        }

        class DecrementCommand{
            constructor(model){
                this.model = model;
            }
            do(){
                this.model.decrement();
            }
            undo(){
                this.model.increment();
            }
        }

        function doIncrement(){
            let incrementCommand = new IncrementCommand(model);
            incrementCommand.do();
            undoStack.push(incrementCommand);
            redoStack = [];
        }

        function doDecrement(){
            let decrementCommand = new DecrementCommand(model);
            decrementCommand.do();
            undoStack.push(decrementCommand);
            redoStack = [];
        }

        function undo(){
            if(undoStack.length == 0) return;
            let command = undoStack.splice(undoStack.length-1, 1)[0];
            command.undo();
            redoStack.push(command);
        }

        function redo(){
            if(redoStack.length == 0) return;
            let command = redoStack.splice(redoStack.length-1, 1)[0];
            command.do();
            undoStack.push(command);
        }


    </script>

</body>
</html>