<!DOCTYPE html><html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ var b=document.getElementById('txt1').value; var c=document.getElementById('txt2').value; var a=document.getElementById('select').value; var add; switch(a) {case "+": add=parseInt(b)+parseInt(c); break; case "-": add=parseInt(b)-parseInt(c); break; case "*": add=parseInt(b)*parseInt(c); break; case "/": add=parseInt(b)/parseInt(c); break;} document.getElementById(b).value=add; } </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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