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                        /JavaScript入門篇

大神們，最后一個按鈕無法運行，幫幫忙

<!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(wǎng)頁添加動態(tài)效果并實現(xiàn)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(chǔ)語法、函數(shù)、數(shù)組、事件、內(nèi)置對象、BOM瀏覽器、DOM操作。</p>
??????? <p>3. 學完以上兩門基礎(chǔ)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="changecolor()" > ?
??? <input type="button" value="改變寬高" onClick="changesize()" >
??? <input type="button" value="隱藏內(nèi)容" onClick="hidetext()">
??? <input type="button" value="顯示內(nèi)容" onClick="showtext()">
??? <input type="button" value="取消設(shè)置" onClick="resttext()">
? </form>
? <script type="text/javascript">
??? var mytxt=document.getElementById("txt");
//定義"改變顏色"的函數(shù)
??? function changecolor()
??????? {
??????????? mytxt.style.color="red";
??????????? mytxt.style.backgroundColor="#ccc";
??????? }
//定義"改變寬高"的函數(shù)
??? function changesize()
??????? {
??????????? mytxt.style.width="300px";
??????????? mytxt.style.height="300px";
??????? }
//定義"隱藏內(nèi)容"的函數(shù)
??? function hidetext()
??????? {
??????????? mytxt.style.display="none";
??????? }
//定義"顯示內(nèi)容"的函數(shù)
??? function showtext()
??????? {
??????????? mytxt.style.display="block";
??????? }
//定義"取消設(shè)置"的函
??? function resttext()
??????? {
??????????? var mychose=confrim("確認重置嗎？");
???????????? if(mychose==ture)
??????????????? {
??????????????????? mytxt.removeAttribute("style");
??????????????? }
??????? }

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