前端设计模式 备忘录模式

// 状态备忘
class Memento {
    constructor(content) {
        this.content = content;
    }
    getContent() {
        return this.content;
    }
}

// 备忘列表
class CareTaker {
    constructor() {
        this.list = [];
    }
    add(memento) {
        this.list.push(memento);
    }
    get(index) {
        return this.list[index]
    }
}

// 编辑器
class Editor {
    constructor() {
        this.content = null;
    }
    setContent(content) {
        this.content = content;
    }
    getContent() {
        return this.content;
    }
    saveContentToMemento() {
        return new Memento(this.content);
    }
    getContentFromMemento(memento) {
        this.content = memento.getContent();
    }
}

// 测试代码
let editor = new Editor();
let careTaker = new CareTaker();
editor.setContent(‘111‘);
editor.setContent(‘222‘);
careTaker.add(editor.saveContentToMemento());// 存储备忘录
editor.setContent(‘333‘);
careTaker.add(editor.saveContentToMemento());// 存储备忘录
editor.setContent(‘444‘);

console.log(editor.getContent());
editor.getContentFromMemento(careTaker.get(1)); // 撤销
console.log(editor.getContent());
editor.getContentFromMemento(careTaker.get(0)); // 撤销
console.log(editor.getContent());