                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript入門篇

多個事件無響應，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課程</H2>
? <div id="txt">
???? <h5>JavaScript為網頁添加動態效果并實現與用戶交互的功能。</h5>
??????? <p>1. JavaScript入門篇，讓不懂JS的你，快速了解JS。</p>
??????? <p>2. JavaScript進階篇，讓你掌握JS的基礎語法、函數、數組、事件、內置對象、BOM瀏覽器、DOM操作。</p>
??????? <p>3. 學完以上兩門基礎課后，在深入學習JavaScript的變量作用域、事件、對象、運動、cookie、正則表達式、ajax等課程。</p>
? </div>
? <form>
? 
??? <input type="button" value="改變顏色" onclick="setColor()"> ?
??? <input type="button" value="改變寬高" onclick="setSize()">
??? <input type="button" value="隱藏內容" onclick="hidden()">
??? <input type="button" value="顯示內容" onclick="visible()">
??? <input type="button" value="取消設置" onClick="confirm()">
? </form>
? <script type="text/javascript">
??? //定義"改變顏色"的函數
??? function setColor()
??? {
??????? let target = document.getElementById("con");
??????? target.style.color = "green";
??????? target.style.backgroundColor = "blue";
??? }
?? ?
??? //定義"改變寬高"的函數
??? function setSize()
??? {
??????? let target = document.getElementById("txt");
??????? target.style.width = "300px";
??????? target.style.height = "300px";
?????? ?
??? }
?? ?
??? //定義"隱藏內容"的函數
??? function hidden()
??? {
??????? let target = document.getElementById("txt");
??????? target.style.display = "none";
??? }
?? ?
??? //定義"顯示內容"的函數
?? ?
??? function visible()
??? {
??????? let target = document.getElementById("txt");
??????? target.style.display = "block";
??? }
?? ?
??? //定義"取消設置"的函數
??? function confirm(){
?? ?
??????? let target = document.getElementById("txt");
??????? let confirm = confirm("是否取消設置");
??????? if(confirm == true)
??????? {
??????????? target.removeAttribute('style');
??????? }
??????? else{
??????????? return;
??????? }
}

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