JavaScript 語法 JavaScript 語法      資料型態 (Data Types)      運算子 (Operators)

<script>
     // ... JavaScript 程式碼 ... 
  function mOver(xx) { xx.style.color = "red";  xx.innerHTML = "停留在此"}
  function mOut(xx) { xx.style.color = "blue";  xx.innerHTML = "已經移走"}
</script>
<span onmouseover="mOver(this)" onmouseout="mOut(this)" style="background-color:#ee9">
  請移過來
</span>
  

   檔案代碼：( 使用 JavaScript 存取和操作 HTML 元素的範例 ) 
<form id="form1" action="#JSoutput">
   <button id="btn" name="按鈕01" type="submit" value="OK" style="color:#a00">
     提交 
   </button>
</form>
<button onclick="disableEmt()"> 禁用上面按鈕 </button>
<button onclick="enableEmt()"> 啟用上面按鈕 </button>
<button onclick="Fn1()"> 取得元素名稱 </button> <span id="d1"></span> <br>
<button onclick="Fn2()"> 取得元素類型 </button> <span id="d2"></span> <br>
<button onclick="Fn3()"> 取得元素的值 </button> <span id="d3"></span> <br>
<button onclick="Fn4()"> 取得元素上的文字 </button> <span id="d4"></span> <br>
<button onclick="Fn5()"> 取得元素的ID </button> <span id="d5"></span> <br>
<button onclick="Fn6()"> 元素所屬表單的ID </button> <span id="d6"></span><br>
<button onclick="Fn7()"> 元素的innerHTML,顯示innerHTML</button>
                            <span id="d7"></span><br>
<button onclick="Fn71()"> 元素的innerText,顯示innerHTML</button>
                            <span id="d71"></span><br>
<button onclick="Fn8()"> 元素的innerText(文字),顯示innerText</button>
                            <span id="d8"></span><br>
<button onclick="Fn81()"> 元素的innerHTML,顯示innerText</button>
                            <span id="d81"></span><br>
<script>
  function disableEmt() {        //禁用元素
    document.getElementById("btn").disabled = true; }
  function enableEmt() {         //啟用元素
    document.getElementById("btn").disabled = false; }
  function Fn1() {               //取得元素名稱
    var x = document.getElementById("btn").name;
    document.getElementById("d1").innerHTML = x; }
  function Fn2() {
    var x = document.getElementById("btn").type;
    document.getElementById("d2").innerHTML = x; }
  function Fn3() {
    var x = document.getElementById("btn").value;
    document.getElementById("d3").innerHTML = x; }
  function Fn4() {
    var x = document.getElementById("btn").innerHTML;
    document.getElementById("d4").innerHTML = x; }
  function Fn5() {
    var x = document.getElementById("btn").id;
    document.getElementById("d5").innerHTML = x; }
  function Fn6() {
    var x = document.getElementById("btn").form.id;
    document.getElementById("d6").innerHTML = x; }
  function Fn7() {         //取得表單id="form1"內的innerHTML,顯示innerHTML
    var x = document.getElementById("form1").innerHTML;
    document.getElementById("d7").innerHTML = x; }
  function Fn71() {        //取得表單id="form1"內的innerText,顯示innerHTML
    var x = document.getElementById("form1").innerText;
    document.getElementById("d71").innerHTML = x; }
  function Fn8() {         //取得表單id="form1"的innerText(文字),顯示innerText
    var x = document.getElementById("form1").innerText;
    document.getElementById("d8").innerText = x; }
  function Fn81() {        //取得表單id="form1"的innerHTML,顯示innerText
    var x = document.getElementById("form1").innerHTML;
    document.getElementById("d81").innerText = x; }
</script>

 var x;
 x = 100;
也可以在宣告變數的同時 指定值：
 var x = 100;