javascript ES6中的命令模式
对于我正在开发的应用程序,我需要实现支持撤销/重做操作的命令模式。我还想使用javascript ES6的新特性,如类、常量等。 我从来没有使用过这个模式,因此我真的很有兴趣听到使用javascript es6语法可以很好地实现这个模式 在Google上阅读了这个模式之后,为了简单起见,我用一个只有两种命令类型(update和delete)和一个模拟数据库的小示例编写了自己的实现 在任何情况下,请随时批评/纠正 mockupDB.jsjavascript ES6中的命令模式,javascript,design-patterns,ecmascript-6,command,Javascript,Design Patterns,Ecmascript 6,Command,对于我正在开发的应用程序,我需要实现支持撤销/重做操作的命令模式。我还想使用javascript ES6的新特性,如类、常量等。 我从来没有使用过这个模式,因此我真的很有兴趣听到使用javascript es6语法可以很好地实现这个模式 在Google上阅读了这个模式之后,为了简单起见,我用一个只有两种命令类型(update和delete)和一个模拟数据库的小示例编写了自己的实现 在任何情况下,请随时批评/纠正 mockupDB.js // mockupDB.js export defaul
// mockupDB.js
export default {
key1: "value1",
key2: "value2",
key3: "value3"
}
Command.js
// Command.js
import mockupDB from "./mockupDB";
class Command {
constructor(execute, undo, serialize, value) {
this.execute = execute;
this.undo = undo;
this.serialize = serialize;
this.value = value;
}
}
export function UpdateCommand(key, value) {
let oldValue;
const execute = () => {
if (mockupDB.hasOwnProperty(key)) {
oldValue = mockupDB[key];
mockupDB[key] = value;
}
};
const undo = () => {
if (oldValue) {
mockupDB[key] = oldValue;
}
};
const serialize = () => {
return JSON.stringify({type: "Command", action: "update", key: key, value: value});
};
return new Command(execute, undo, serialize, value);
}
export function DeleteCommand(key) {
let oldValue;
const execute = () => {
if (mockupDB.hasOwnProperty(key)) {
oldValue = mockupDB[key];
delete mockupDB[key];
}
};
const undo = () => {
mockupDB[key] = oldValue;
};
const serialize = () => {
return JSON.stringify({type: "Command", action: "delete", key: key});
};
return new Command(execute, undo, serialize);
}
CommandManager.js
// CommandManager.js
export class CommandManager {
constructor() {
this.executeHistory = [];
this.undoHistory = [];
}
execute(command) {
this.executeHistory.push(command);
command.execute();
console.log(`Executed command ${command.serialize()}`);
}
undo() {
let command = this.executeHistory.pop();
if (command) {
this.undoHistory.push(command);
command.undo();
console.log(`Undo command ${command.serialize()}`)
}
}
redo() {
let command = this.undoHistory.pop();
if (command) {
this.executeHistory.push(command);
command.execute();
console.log(`Redo command ${command.serialize()}`);
}
}
}
client.js
// client.js
import {CommandManager} from "./CommandManager";
import {UpdateCommand, DeleteCommand} from "./Command";
import mockupDB from "./mockupDB";
"use strict";
const main = () => {
const commandManager = new CommandManager();
console.log("DB status", mockupDB, "\n");
commandManager.execute(new UpdateCommand("key2", "newValue2"));
commandManager.execute(new DeleteCommand("key3"));
console.log("DB status", mockupDB, "\n");
commandManager.undo();
commandManager.undo();
console.log("DB status", mockupDB, "\n");
commandManager.redo();
commandManager.redo();
console.log("DB status", mockupDB, "\n");
};
main();
输出
DB status { key1: 'value1', key2: 'value2', key3: 'value3' }
Executed command {"type":"Command","action":"update","key":"key2","value":"newValue2"}
Executed command {"type":"Command","action":"delete","key":"key3"}
DB status { key1: 'value1', key2: 'newValue2' }
Undo command {"type":"Command","action":"delete","key":"key3"}
Undo command {"type":"Command","action":"update","key":"key2","value":"newValue2"}
DB status { key1: 'value1', key2: 'value2', key3: 'value3' }
Redo command {"type":"Command","action":"update","key":"key2","value":"newValue2"}
Redo command {"type":"Command","action":"delete","key":"key3"}
DB status { key1: 'value1', key2: 'newValue2' }