知识点：
1.从input中取值：
var a=parseInt(document.getElementById(\'num1\').value);
2.把数值放回input中
document.getElementById(\'result\').value=a+b;
1 <html> 2 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 5 <style> 6 input{ 7 width:50px; 8 } 9 </style> 10 <script type="text/javascript"> 11 function calc() { 12 // body... 13 var a = parseInt(document.getElementById(\'num1\').value); 14 var b = parseInt(document.getElementById(\'num2\').value); 15 document.getElementById(\'result\').value = a + b; 16 } 17 </script> 18 </head> 19 20 <body><input type="text" id="num1"> + 21 <input type="text" id="num2"> 22 = 23 <input type="text" id="result"> 24 <input type="button" value="计算" onclick="calc()"></body> 25 26 </html>
效果图：