js设计模式——5.状态模式

js设计模式——5.状态模式

　　

代码演示

/*js设计模式——状态模式*/

// 状态（红灯，黄灯，绿灯）
class State {
    constructor(color) {
        this.color = color;
    }

    handle(context) {
        console.log(`turn to ${this.color} light`);
        context.seState(this);
    }
}

// 主体
class Context {
    constructor() {
        this.state = null;
    }

    getState() {
        return this.state;
    }

    seState(state) {
        this.state = state;
    }
}

// test
let context = new Context()
let green = new State('green')
let yellow = new State('yellow')
let red = new State('red')

// 绿灯亮了
green.handle(context)
console.log(context.getState())

// 红灯亮了
red.handle(context)
console.log(context.getState())

// 黄灯亮了
yellow.handle(context)
console.log(context.getState())

引入javascript-state-machine示例

/*有限状态机*/
import StateMachine from 'javascript-state-machine'
import $ from 'jquery'

let fsm = new StateMachine({
    init: '收藏', // 初始化状态，带收藏
    transitions : [
        {
            name : 'doState',
            form : '收藏',
            to : '取消收藏'
        },
        {
            name : 'deleteState',
            form : '取消收藏',
            to : '收藏'
        }
    ],
    methods : {
        // 执行收藏
        onDoState : function () {
            alert('收藏成功')
            updateText()
        },

        // 取消收藏
        onDeleteState: function () {
            alert('已取消收藏')
            updateText()
        }
    }
})

let $btn = $('btn1')

$btn.click(function () {
    if(fsm.is('收藏')){
        fsm.doState()
    } else {
        fsm.deleteState()
    }
})

// 更新方案
function updateText() {
    $btn.text(fsm.state)
}
// 初始化方案
updateText()

以promise示例来演示

// promise 状态机模型
import StateMachine from 'javascript-state-machine';

let prmiseFsm = new StateMachine({
    init: 'pending', // 初始化状态
    transitions: [
        {
            name: 'resolve',
            from: 'pending',
            to: 'fullfilled',
        },
        {
            name: 'reject',
            from: 'pending',
            to: 'rejected',
        },
    ],
    methods: {
        // 监听 resolve
        onResolve: function (state, data) {
            // state —— 当前状态机示例 data - fsm.resolve(xxx) 传递的参数
            data.succesList.forEach(fn => fn())
        },

        // 监听 reject
        onReject: function (state, data) {
            // state —— 当前状态机示例 data - fsm.reject(xxx) 传递的参数
            data.failList.forEach(fn => fn())
        },

    },
});

// 定义 Promise
class MyPromise {
    constructor(fn) {
        this.succesList = []
        this.failList = []

        fn(function () {
            // resolve 函数
            fsm.resolve(this)
        }, function () {
            // reject 函数
            fsm.reject(this)
        });
    }

    then(succesFn, failFn) {
        this.succesList.push(succesFn)
        this.failList.push(failFn)
    }
}

// 测试代码
function loadImg(src) {
    const promise = new Promise(function (resolve, reject) {
        let img = document.createElement('img');
        img.onload = function () {
            resolve(img);
        };
        img.onerror = function () {
            reject();
        };
        img.src = src;
    });
    return promise;
}

let src = 'http://img2.imgtn.bdimg.com/it/u=234634259,4236876085&fm=26&gp=0.jpg';
let result = loadImg(src);

result.then(function () {
    console.log('ok1');
}, function () {
    console.log('fail1');
});

result.then(function () {
    console.log('ok2');
}, function () {
    console.log('fail2');
});