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();
}
}
