前端设计模式——命令模式

// 定义一个命令对象
class Command {
  constructor(receiver, args) {
    this.receiver = receiver;
    this.args = args;
    this.executed = false;
  }
  
  execute() {
    if (!this.executed) {
      this.receiver.execute(this.args);
      this.executed = true;
    }
  }
  
  undo() {
    if (this.executed) {
      this.receiver.undo(this.args);
      this.executed = false;
    }
  }
}

// 定义一个接收者对象
class Receiver {
  constructor() {
    this.value = 0;
  }
  
  execute(args) {
    this.value += args;
    console.log(`执行操作，value = ${this.value}`);
  }
  
  undo(args) {
    this.value -= args;
    console.log(`撤销操作，value = ${this.value}`);
  }
}

// 创建一个接收者对象和一些命令对象
const receiver = new Receiver();
const command1 = new Command(receiver, 1);
const command2 = new Command(receiver, 2);
const command3 = new Command(receiver, 3);

// 创建一个历史列表并将命令对象添加到其中
const history = [command1, command2, command3];

// 依次执行命令对象
history.forEach((command) => {
  command.execute();
});

// 撤销最后一个操作
history.pop().undo(); // 撤销操作，value = 3