Simple implementation of three-level linkage using JavaScript-JS Tutorial-php.cn

Simple implementation of three-level linkage using JavaScript

韦小宝

Release： 2018-03-10 11:55:06

Original

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In actual JavaScript project development, we often need three-level linkage, such as the selection of provinces and municipalities, the selection of three-level classification of goods, etc. Today we will explain how JavaScript implements three-level linkage, and we will share the JavaScript source code with you! If you are not familiar with JavaScript to implement three-level linkage, you can take a look with us!

Knowledge points:

1. json.parse() converts the json format string into Object. json.stringify() converts the object into a json format string.

2. Important attribute selectedIndex: Returns the index number of the selected option in the drop-down list.

3. onchangeEvent

The following is the code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>三级联动</title>
</head>
<body>
    <select id="province">
        <!-- <option>北京</option>
        <option>天津</option> -->
    </select>
    <select id="city"></select>
    <select id="count"></select>
    <script type="text/javascript" src="china.js"></script>
    <script type="text/javascript">
    var province = document.getElementById("province");
    var city = document.getElementById("city");
    var count = document.getElementById("count");

    var chinaArea = JSON.parse(chinaArea);//将字符串格式的json数据转换成对象
    // var chinaArea = eval("("+chinaArea+")");
    // var chinaArea = new Function("return " + chinaArea)();

    //1.遍历省份
    var provinceList = chinaArea.china.province;//数组
    for(var i = 0 ; i < provinceList.length; i++) {
        var option = document.createElement("option");
        option.innerHTML = provinceList[i]["-name"];
        province.appendChild(option);
    }

    province.onchange = function() {
        //选择省份之后，市区跟着变化
        cityData();
        countData();
    }
    cityData();
    //市区的数据填充
    var sIndex = 0;
    var cityIndex = 0;
    function cityData() {
        //清除原来的市区信息
        city.innerHTML = "";
        //2.遍历市区
        sIndex = province.selectedIndex;//设置或返回下拉列表备选选项的索引号。
        for(var j = 0; j < provinceList[sIndex].city.length;j++) {
            var option = document.createElement("option");
            option.innerHTML = provinceList[sIndex].city[j]["-name"];
            city.appendChild(option);
        }
    }

    //县区数据填充

    function countData() {
        //清除原来的县区信息
        count.innerHTML = "";

        // 
        cityIndex = city.selectedIndex;
        var countList = chinaArea.china.province[sIndex].city[cityIndex].county; 
        for(var k = 0; k < countList.length; k++) {
            var option = document.createElement("option");
            option.innerHTML = countList[k]["-name"];
            count.appendChild(option);
        }
    }

    city.onchange = function() {
        countData();
    }
    countData();
    </script>
</body>
</html>

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You can combine the source code and Check out the knowledge! Try to write it yourself and strengthen your knowledge!

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