谁能告诉我这样为什么不行
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | <!DOCTYPE html><html> <head> <title> 事件</title> <script type="text/javascript"> function count(){ var one,two,sel,fruit,res; //获取第一个输入框的值 one = parseInt(document.getElementById("txt1").value); //获取第二个输入框的值 two = parseInt(document.getElementById('txt2').value); //获取选择框的值 sel = document.getElementById("select").value; fruit = document.getElementById("fruit").value; //获取通过下拉框来选择的值来改变加减乘除的运算法则 switch(sel){ case '+': res = one+two; break; case '-': res = one-two; break; case '*': res = one*two; break; case '/': res = one/two; } //设置结果输入框的值 fruit = res; <!-- document.getElementById('fruit').value = res; --> } </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> |
