js实现百度，淘宝搜索功能

Common.js

//封装类名

function byClassName(sClassName){
    if(document.getElementsBYClassName){
        return document.getElementsByClassName(sClassName);
    } else {
        var allTagsName = document.getElementsByTagName('*');
        var result = [];
        for(var i = 0; i<allTagsName.length;i++){
            if(allTagsName[i].className === sClassName){
                result.push(allTagsName[i]);
            }
        }
        return result;
    }
}

index.js

var oTxt = byClassName('txt')[0];
var oBtn = byClassName('btn')[0];
var oList = byClassName('list')[0];
oTxt.onpropertychange = oTxt.oninput  = function(){
//    先创建一个script标签,引入接口
    var oScript = document.createElement('script');
    oScript.src = 'https://suggest.taobao.com/sug?code=utf-8&q='+ this.value+'&_ksTS=1519875402602_594&callback=callback';
//    将script标签添加到页面中
    document.body.appendChild(oScript);
//    移除标签
    document.body.removeChild(oScript);
}
//创建回调函数接收数据
function callback(data){
    oList.innerHTML = '';
    data.result.forEach( v => {
        var oLi = document.createElement('li');
        oLi.innerHTML = v;
        oList.appendChild(oLi);
        oLi.onclick = function(){
            oTxt.value = oLi.innerHTML;
            oList.innerHTML = '';
        }
    });
}

HTML（百度）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>百度搜索</title>
    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        form[name=search-form] {
            margin: 40px auto 0;
             640px;
        }
        input[name='search-content'] {
             600px;
            line-height: 30px;
            border:1px solid #ccc;
            vertical-align: bottom;
            outline: none;
        }
        input[name='search-btn'] {
             40px;
            height: 32px;
            border: 1px solid #ccc;
            outline: none;
            cursor: pointer;
        }
        #list {
            list-style: none;
            margin: 0 auto;
             640px;
        }
        #list li {
            padding: 10px 4px;
            border-bottom: 1px dashed #eee;
        }
    </style>
</head>
<body>
    <form action="javascript:;" name="search-form">
        <input type="text" name="search-content"><input type="submit" name="search-btn">
    </form>
    <ul id="list"></ul>
 
    <script>
 
        var oForm = document.forms['search-form'];
 
        var oContent = oForm.elements['search-content'];
 
        var oList = document.getElementById('list');
 
        // 定义回调函数
        function callback(data) {
            oList.innerHTML = '';
            data.s.forEach( v => {
                var oLi = document.createElement('li');
                oLi.innerHTML = v;
 
                oList.appendChild(oLi);
            });
        }
        oContent.onpropertychange = oContent.oninput = function () {
            var oScript =document.createElement('script');
            oScript.src = 'https://sp0.baidu.com/5a1Fazu8AA54nxGko9WTAnF6hhy/su?wd=' + this.value + '&json=1&p=3&sid=1464_25548_21101_18559_17001_20719&req=2&csor=1&cb=callback';
 
            document.body.appendChild(oScript);
            document.body.removeChild(oScript);
        };
    </script>
</body>
</html>

HTML（淘宝）

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>跨域请求数据</title>
<style>
    *{
        margin: 0;
        padding: 0;
    }
    ul li{
        list-style: none;
    }
    form{
         640px;
        margin: 30px auto 0;
        position: relative;
    }
    input{
        box-sizing: border-box;
        outline: none;
    }
    .txt{
         600px;
        line-height: 30px;
        vertical-align: bottom;
        border: 1px solid #ccc;
    }
    .btn{
         40px;
        height: 32px;
        border: 1px solid #ccc;
        cursor: pointer;
    }
    .list{
        position: absolute;
    }
    .list li{
         592px;
        padding: 10px 4px;
        cursor: pointer;
    }
    .list li:hover{
        background: #eee;
    }
</style>
</head>
<body>
    <form action="javascript:;">
        <input class="txt" type="text" /><input class="btn" type="submit" />
    <ul class="list"></ul>
    </form>
    <script src="js/common.js"></script>
    <script src="js/index.js"></script>
</body>
</html>

两者实现思路都是一样的，进入其对应的官方网站，在输入内容看，打开控制面板查看其请求的api接口，然后将api接口复制过来，通过创建回调接受，然后根据输入的文本框的内容进行动态li的创建，删除即可实现。