命令模式的撤销操作

撤销操作的实现一般是给命令对象增加一个名为unexecude或者undo的方法，在该方法里执行execute的反向操作，代码如下：

var MoveCommand = function (receiver,pos) {
    this.receiver = receiver;
    this.pos = pos;
    this.oldPos = null;
};
MoveCommand.prototype.execute = function () {
    this.receiver.start('left',this.pos,1000,'strongEaseOut');
    this.oldPos = this.receiver.dom.getBoundingClienRect()[this.receiver.propertyName];//记录初始位置
};
MoverCommand.prototype.undo = function () {
    this.receiver.start('left',this.oldPos,1000,'strongEaseOut');
    //撤销操作，回到之前运动的位置
};
var moveCommand;
moveBtn.onclick = function() {
    var animate = new Animate(ball);
    moveCommand = new MoveCommand(animate,pos.value);
    moveCommand.execute();
};
cancelBtn.onclick = function () {
    moveCommand.undo();
}

撤销和重做

下面代码将讲述如何撤销一系列的命令

var Ryu = {
    attack :function () {
        console.log('攻击')
    },
    defense:function() {
        console.log('防御')
    },
    jump:function() {
        conosle.log('跳跃')
    },
    crouch:function () {
        console.log('蹲下')
    }
};

var makeCommand = function (receiver,state) {
    return function () {
        receiver[state]();
    }
};
var commands = {
    "119":"jump",
    "115":"crouch",
    "97":"defense",
    "100":"attack"
};
var commandStack = [];
doccument.onkeypress = function (ev) {
    var keyCode = ev.keyCode,
        command = makCommand(Ryu,commands[keyCode]);
    if(command) {
        cammand();
        commandStack.push(command);//保存刚才执行的动作
    }
};
//撤销的操作
document.getElementById('replay').onclick = function () {
    var command;
    while(command = commandStack.shift()) {
        command();
    }
}