和这个....
HTML部分
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="
http://www.w3.org/1999/xhtml"><head>
<meta http-equiv="Content-type" content="text/html;charset=UTF-8" />
<title>ex3</title>
<script type="text/javascript" src="ex3.js"></script>
</head>
<body>
<form>
<p id="output">OUTPUT</p>
<br/>
<textarea name="number1" id="number1" rows="1" cols="10">Number 1</textarea>
+
<textarea name="number2" id="number2" rows="1" cols="10">Number 2</textarea>
<button type="button" onclick="output()">=</button>
</form>
</body>
</html>
JS部分
var num1 = document.getElementById("number1").value;
var num2 = document.getElementById("numebr2").value;
var total = num1 + num2;
function output(){
document.getElementById("output").innerHTML = total;
}
