Satu artikel menerangkan secara terperinci cara melaksanakan menu pautan tiga peringkat dengan JS (dengan penjelasan idea)-tutorial js-php.cn

Idea: Setiap menu lungsur berfungsi sebagai komponen dan boleh menerima set data dan menjana pilihan menu yang berbeza berdasarkan kandungan data yang berbeza. Perkaitan antara ketiga-tiga tahap tersebut dicapai melalui acara lontaran. Data diperolehi dari latar belakang.

Apabila mengklik pada menu wilayah untuk memilih Shaanxi, komponen menu akan membuang wilayah semasa melalui lontaran acara. Selepas mengetahui wilayah, anda boleh mendapatkan data bandar di bawah wilayah dari latar belakang. Dan seterusnya. [Cadangan berkaitan: Tutorial video JavaScript]

Kesan pencapaian:

bahagian hadapan dan antara muka bahagian belakang Maklumat:

Antara muka menu lata tiga peringkat:

## URL: http://10.9.72.245:4010

## Kaedah: "GET"

## Format data:

Permintaan: QueryString

Respons: JSON

Nama antara muka:

1 . http:// 10.9.72.245:4010/getProvince

2. http://10.9.72.245:4010/getCity

3. http://10.9.72.245:4010/getCo

Dapatkan antara muka wilayah

Nama antara muka:/getProvince

Permintaan: Tiada parameter

Respons: {"province":["Beijing","Tianjin ","Hebei" ,...]}

Dapatkan antara muka bandar:

Nama antara muka: /getCity

Permintaan:?province="Hebei"

Maklum balas: { "bandar":["Shijiazhuang", "Tangshan", "Qinhuangdao",...]}

Dapatkan antara muka daerah:

Nama antara muka: /getCounty

Permintaan ：?city="Shijiazhuang"

Respons: {"county":["Daerah Chang'an", "Daerah Qiaodong", "Daerah Qiaoxi",...]}

Pelaksanaan khusus :

1. Buat komponen menu lungsur dan komunikasi bahagian hadapan dan belakang:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script type="module">
        import QueryString from &#39;./js/QueryString.js&#39;;
        import DropDownMemu from &#39;./js/DropDownMemu.js&#39;;
 
        let cityInfo = {};
        init();
        function init(){
            ajax("http://10.9.72.245:4010","getProvince").then(succeseFunction).catch(failFunction);
        }
        // ajax通信成功后执行：
        function succeseFunction(_data){
            let data = JSON.parse(_data);
            let key = Object.keys(data)[0];
            data = Object.values(data)[0];
            if(DropDownMemu.Obj[key]){
                DropDownMemu.Obj[key].list = data;
                DropDownMemu.Obj[key].name = data[0];
            }else{
                let memu = new DropDownMemu(key);
                memu.addEventListener("change",changeHandler);
                memu.list = data;
                memu.name =data[0];
                memu.appendTo("body");
                cityInfo[key] = data[0];
            }
        }
        // 当菜单显示内容改变时接收到菜单抛发出的事件并获取事件中携带的信息例如{"province":"陕西"}或者{"city":"西安"}
        function changeHandler(e){
            let key = e.currentTarget.label;
            cityInfo[key] = e.data[key];
            let interfaceName;
            if(e.data.province){
                interfaceName = "getCity";
            }else if(e.data.city){
                interfaceName = "getCounty";
            }else{
                return
            }
            ajax("http://10.9.72.245:4010",interfaceName,cityInfo).then(succeseFunction).catch(failFunction);
        }
        /*
            ajax通信：
            参数列表：
            url: 后台服务地址
            interfaceType：接口类型，如 "getProvince"
            data:传输的数据,例如:{"province":"陕西"}
            通信类型type:默认"GET"请求
            是否以json格式发送数据：默认为false
        */
        function ajax(url,interfaceType,data,type="get",json=false){
            type = type.toUpperCase();
            let o = type==="GET"? null : data;
            if(data) data = json? JSON.stringify(data) : QueryString.stringify(data);
            else data = "";
            return new Promise(function(resolve,reject){
                let xhr = new XMLHttpRequest();
                xhr.open(type,url + "/" + interfaceType + (type==="GET"? "?"+data : ""));
                xhr.send(o);
                xhr.onreadystatechange = function(){
                    if(xhr.readyState===4 && xhr.status===200){
                        resolve(xhr.response);
                    }else if(xhr.readyState===4){
                        resolve(xhr.status);
                    }
                }
                xhr.onerror= function(){
                    reject(xhr.response);
                }
            })
        }
        // ajax通信失败时执行
        function failFunction(_err){
            console.log(_err);
        }
 
 
    </script>
</body>
</html>

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2

import Component from "./Component.js";

export default class DropDownMemu extends Component {

    _list;      // 当前下拉菜单的可选项。
    _name;      // 当前选择显示的名字例如： "北京"
    label;      // 当前下拉菜单的标签，province city county
    spanLabel;  // 标签容器
    spanCaret;  // 三角形
    ul;         // 下拉选项容器
    bool=false; // 控制鼠标事件，聚焦状态或正在选择时，不触发鼠标划入滑出效果。
    
    // 根据不同的状态设置下拉菜单的样式。
    static DROPDOWN = Symbol();
    static DEFAULT = Symbol();
    // 静态全局变量 每创建一个下拉菜单，都存储到这个对象中，全局管理创建的每一个下拉菜单。
    static Obj = {};

    constructor(_label) {
        super("p");
        this.label = _label;
        // 创建HTML结构
        this.render();
        // 设置样式
        this.setStyle();
        // 鼠标滑入滑出点击，聚焦失焦，点击事件
        this.elem.addEventListener("focusin", e =>this.mouseHandler(e));
        this.elem.addEventListener("focusout", e =>this.mouseHandler(e));
        this.elem.addEventListener("mouseenter", e=>this.mouseHandler(e));
        this.elem.addEventListener("mouseleave", e=>this.mouseHandler(e));
        this.elem.addEventListener("click", e => this.mouseHandler(e));
    }
    
    mouseHandler(e){
        switch(e.type){
            case "mouseenter": 
                if(this.bool) return
                this.elem.style.backgroundColor = "#e6e6e6";
                break;
            case "mouseleave":
                if(this.bool) return
                this.elem.style.backgroundColor = "#fff";
                break;
            case "focusin":
                this.setState(DropDownMemu.DROPDOWN);
                this.bool = true;
                break;
            case "focusout":
                this.setState(DropDownMemu.DEFAULT);
                this.bool = false;
            case "click" :
                if(e.target.constructor !== HTMLLIElement) return
                this._name = e.target.textContent;
                // 当点击时修改当前显示的内容，重设样式，并抛发事件告知外部当前的内容。
                this.setContent();
                let evt = new FocusEvent("focusout");
                this.elem.dispatchEvent(evt);
        }
    }
    
    set name(_name){
        this._name = _name;
        this.setContent();
    }
    get name(){
        return this._name;
    }
    set list(_list){
        this._list = _list;
        this.ul.innerHTML = "";
        this.ul.appendChild(this.createLi());
    }
    // 修改菜单当前显示的内容并并抛发数据
    setContent(_name){
        this._name = _name || this._name;
        this.spanLabel.textContent = this._name;
        let evt = new MouseEvent("change");
        if(!evt.data) evt.data = {}
        evt.data[this.label] = this._name;
        this.dispatchEvent(evt);
    }
    // 根据指定的list创建下拉菜单选项。
    createLi(_list){
        this._list = _list || this._list;
        let elem = document.createDocumentFragment();
        this._list.forEach((item, index) => {
            let li = document.createElement("li");
            li.textContent = item;
            Object.assign(li.style, {
                lineHeight:"26px",
                padding:"0 15px",
            })
            elem.appendChild(li);
        })
        return elem;
    }
    setState(type){
        switch(type){
            case DropDownMemu.DROPDOWN:
                this.elem.style.backgroundColor = "#e6e6e6";
                this.ul.style.display = "block";
                break;
            case DropDownMemu.DEFAULT:
                this.elem.style.backgroundColor = "#fff";
                this.ul.style.display = "none";
                break;
        }
    }
    appendTo(parent){
        super.appendTo(parent);
        DropDownMemu.Obj[this.label] = this;
    }
    render() {
        this.elem.setAttribute("tabIndex",1);
        this.spanLabel = document.createElement("span");
        this.spanCaret = document.createElement("span");
        this.ul = document.createElement("ul");
        this.elem.appendChild(this.ul);
        this.spanLabel.textContent = this._name;
        this.elem.appendChild(this.spanLabel);
        this.elem.appendChild(this.spanCaret);
    }
    setStyle() {
        Object.assign(this.elem.style, {
            float: "left",
            minHeight: "20px",
            minWidht: "80px",
            color: "#333",
            fontWeight: "normal",
            textAlign: "center",
            whiteSpace: "nowrap",
            verticalAlign: "middle",
            cursor: "pointer",
            border: "1px solid #ccc",
            borderRadius: "4px",
            backgroundColor: "#fff",
            padding: "6px 12px",
            fontSize: "14px",
            userSelect: "none",
            marginRight: "100px",
            position:"relative",
        });
        Object.assign(this.spanLabel.style, {
            float: "left",
            padding: "0 5px"
        })
        Object.assign(this.spanCaret.style, {
            display: "inline-block",
            verticalAlign: "middle",
            borderTop: "4px dashed",
            borderRight: "4px solid transparent",
            borderLeft: "4px solid transparent",
        })
        Object.assign(this.ul.style, {
            listStyle: "none",
            position: "absolute",
            top: "100%",
            left: "0",
            zIndex: "1000",
            minWidth: "100px",
            padding: "5px 0px",
            margin: "2px 0 0",
            fontSize: "14px",
            textAlign: "left",
            backgroundColor: "#fff",
            border: "1px solid rgba(0, 0, 0, 0.15)",
            borderRadius: "4px",
            boxShadow: "0 6px 12px rgba(0, 0, 0, 0.175)",
            display: "none",
        })
    }
}

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3. Kelas induk komponen:

export default class Component extends EventTarget{
    elem;
    constructor(_type){
        super();
        this.elem = this.createElem(_type);
    }
    createElem(_type){
        let elem = document.createElement(_type);
        return elem;
    }
    appendTo(parent){
        if(typeof parent==="string") parent = document.querySelector(parent);
        parent.appendChild(this.elem);
    }
}

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4 perkhidmatan latar belakang nodejs:

let http = require("http");
let querystring = require("querystring");
let data,
    req,
    res;

// 读取所有城市数据并解析为对象，同步读取。
let fs = require("fs");
let allCityInfo = JSON.parse(fs.readFileSync(&#39;./city.json&#39;));

let server = http.createServer(listenerHandler);
server.listen(4010,"10.9.72.245",listenerDoneHandler);

function listenerHandler(_req,_res){
    req = _req;
    res = _res; 
    res.writeHead(200,{
        "content-type":"text/html;charset=utf-8",
        "Access-Control-Allow-Origin":"*",
        "Access-Control-Allow-Headers":"*",
    });
    data="";
    req.on("data",function(_data){
        data=_data;
    })
    req.on("end",receiveHandler);
}
function receiveHandler(){
    // console.log(allCityInfo);
    // 根据请求头的url解析接口类型
    let type = req.url.trim().split("?")[0].replace(/\//g,"");
    console.log(type);
    // 根据请求头的url解析传入的参数
    if(req.method.toUpperCase()==="GET"){
        if(req.url.includes("favicon.ico")) return res.end();
        else data = req.url.includes("?") ? req.url.split("?")[1] : "";
    }
    try{
        data = JSON.parse(data);
    }catch{
        data = querystring.parse(data);
    }
    console.log(data);

    // 根据接口类型查找数据。
    let list = {};
    switch(type){
        case "getProvince":
            list.province = Object.keys(allCityInfo);
            break;
        case "getCity" :
            list.city = Object.keys(allCityInfo[data.province]);
            break;
        case "getCounty":
            list.county = allCityInfo[data.province][data.city];
            break;
    }

    console.log(list);
    res.write(JSON.stringify(list));
    res.end()
}
function listenerDoneHandler(){
    console.log("开启服务成功");
}

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5 format json, seperti yang ditunjukkan di bawah:

{

"Beijing": {

"Beijing": ["Daerah Dongcheng", "Daerah Xicheng", "Daerah Chongwen", "Daerah Xuanwu" , "Daerah Chaoyang", "Daerah Fengtai", "Daerah Shijingshan", "Daerah Haidian", "Daerah Mentougou", "Daerah Fangshan", "Daerah Tongzhou", "Daerah Shunyi", "Daerah Changping", "Daerah Daxing" , "Daerah Pinggu", "Daerah Huairou", "Kaunti Miyun", "Kaunti Yanqing", "Lain-lain"]

},

"Tianjin": {

"Tianjin": ["Daerah Heping", "Daerah Hedong", "Daerah Hexi", "Daerah Nankai", "Daerah Hebei", "Daerah Hongjie", "Daerah Baru Binhai", "Daerah Dongli", " Daerah Xiqing", "Daerah Jinnan", "Daerah Beichen", "Daerah Ninghe", "Daerah Wuqing", "Kaunti Jinghai", "Daerah Baodi", "Jixian", "Daerah Tanggu", "Daerah Hangu" ", " Daerah Dagang", "Daerah Baodi", "Lain-lain"]

},

}

Atas ialah kandungan terperinci Satu artikel menerangkan secara terperinci cara melaksanakan menu pautan tiga peringkat dengan JS (dengan penjelasan idea). Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!