<!DOCTYPE html> <html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ var result=""; var x1 = document.getElementById("tx1").value; var x2 = document.getElementById("tx2").value; var x3 = document.getElementById("select").value; switch (x3){ case "+" : result=parseInt(x1)+parseInt(x2); case "-" : result=parseInt(x1)-parseInt(x2); case "*" : result=parseInt(x1)*parseInt(x2); case "/" : result=parseInt(x1)/parseInt(x2); } document.getElementById("fruit").value=result; //获取第一个输入框的值 //获取第二个输入框的值 //获取选择框的值 //获取通过下拉框来选择的值来改变加减乘除的运算法则 //设置结果输入框的值 } </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>
switch~case:要有break来结束运行,不然会重头执行到尾