<!doctype html> <html> <head> <meta charset="utf-8"> <title>计算机</title> </head> <body> <input id="firstnumber" type="text" placeholder="请输入第一个值"/> <select id="choice" name="choice" > <option value=1>+</option> <option value=2>-</option> <option value=3>*</option> <option value=4>/</option> </select> <input id="secondnumber" type="text" placeholder="请输入第二个值"/> <input type="button" value="计算" onClick="show();"/> <label id="result"></label> <script type="text/javascript"> function show(){ var first = parseInt(document.getElementById("firstnumber").value); var second =parseInt(document.getElementById("secondnumber").value); var chioce = document.getElementById("choice"); //可以获取下拉列表中选中的值 var symbol = chioce.options[chioce.selectedIndex].text; var result; if(symbol=='+'){ result = first+second; } else if(symbol=='-'){ result = first-second; }else if(symbol == '*'){ result = first*second; } else if(symbol == '/'){ result = first/second; } //可以将值放入标签里面 document.getElementById("result").innerHTML=result; } </script> </body> </html>
效果图：
