<!DOCTYPE html><html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title> 事件</title> <script type="text/javascript"> function count(){ var a=document.getElementById("txt1").value; var b=document.getElementById("txt2").value; var c=document.getElementById("select").value; var d=""; switch(c) { case "+":d=parseInt(a)+parseInt(b); break; case "-":d=a-b; break; case "*":d=a*b; break; case "/":d=a/b; break; } d=document.getElementById("fruit").value; } </script> </head> <body> <input type='text' id='txt1' /> <select id='select'> <option value='+'>+</option> <option value="-">-</option> <option value="*">*</option> <option value="/">/</option> </select> <input type='text' id='txt2' /> <input type='button' value=' = ' onclick="count()"/> <!--通过 = 按钮来调用创建的函数，得到结果--> <input type='text' id='fruit' /> </body></html>
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