                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript入门篇

多个事件无响应，求教各位猿兄

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" Content="text/html; charset=utf-8" />
<title>javascript</title>
<style type="text/css">
body{font-size:12px;}
#txt{
    height:400px;
    width:600px;
   border:#333 solid 1px;
   padding:5px;}
p{
   line-height:18px;
   text-indent:2em;}
</style>
</head>
<body>
<h2 id="con">JavaScript课程</H2>
<div id="txt">
     <h5>JavaScript为网页添加动态效果并实现与用户交互的功能。</h5>
        <p>1. JavaScript入门篇，让不懂JS的你，快速了解JS。</p>
        <p>2. JavaScript进阶篇，让你掌握JS的基础语法、函数、数组、事件、内置对象、BOM浏览器、DOM操作。</p>
        <p>3. 学完以上两门基础课后，在深入学习JavaScript的变量作用域、事件、对象、运动、cookie、正则表达式、ajax等课程。</p>
</div>
<form>

    <input type="button" value="改变颜色" onclick="setColor()">
    <input type="button" value="改变宽高" onclick="setSize()">
    <input type="button" value="隐藏内容" onclick="hidden()">
    <input type="button" value="显示内容" onclick="visible()">
    <input type="button" value="取消设置" onClick="confirm()">
</form>
<script type="text/javascript">
    //定义"改变颜色"的函数
    function setColor()
    {
        let target = document.getElementById("con");
        target.style.color = "green";
        target.style.backgroundColor = "blue";
    }

    //定义"改变宽高"的函数
    function setSize()
    {
        let target = document.getElementById("txt");
        target.style.width = "300px";
        target.style.height = "300px";

    }

    //定义"隐藏内容"的函数
    function hidden()
    {
        let target = document.getElementById("txt");
        target.style.display = "none";
    }

    //定义"显示内容"的函数

    function visible()
    {
        let target = document.getElementById("txt");
        target.style.display = "block";
    }

    //定义"取消设置"的函数
    function confirm(){

        let target = document.getElementById("txt");
        let confirm = confirm("是否取消设置");
        if(confirm == true)
        {
            target.removeAttribute('style');
        }
        else{
            return;
        }
}

</script>
</body>
</html>