备忘录模式Memento Pattern
是在不破坏封装性的前提下,将对象当前的内部状态保存在对象之外,以便以后当需要时能将该对象恢复到原先保存的状态。备忘录模式又叫快照模式,是一种对象行为型模式。
备忘录模式是关于捕获和存储对象的当前状态的方式,以便以后可以平滑地恢复它。
// 以文本编辑器为例,该编辑器会不时地保存状态,并且可以根据需要进行恢复。
class EditorMemento { // memento对象将能够保持编辑器状态
constructor(content) {
this._content = content;
}
getContent() {
return this._content;
}
}
class Editor {
constructor(){
this._content = "";
}
type(words) {
this._content = `${this._content} ${words}`;
}
getContent() {
return this._content;
}
save() {
return new EditorMemento(this._content);
}
restore(memento) {
this._content = memento.getContent();
}
}
(function(){
const editor = new Editor()
editor.type("This is the first sentence.");
editor.type("This is second.");
const saved = editor.save();
editor.type("And this is third.")
console.log(editor.getContent()); // This is the first sentence. This is second. And this is third.
editor.restore(saved);
console.log(editor.getContent()); // This is the first sentence. This is second.
})();
https://github.com/WindrunnerMax/EveryDay
https://github.com/Byronlee/Design-patterns
https://www.runoob.com/design-pattern/memento-pattern.html
https://github.com/sohamkamani/javascript-design-patterns-for-humans#-memento