var req1, req2;
var sumq ="";
function add(){
sumq = req1 + req2;
return sumq;
}
function substracte(){
sumq = req1 - req2;
return sumq;
}
function multiplication(){
sumq = req1 * req2;
return sumq;
}
function division(){
sumq = req1 / req2;
}
function count(){
req1 = document.getElementById("txt1").value;
req2 = document.getElementById("txt2").value;
var symbol = document.getElementById("select").vlaue;
if(symbol =='+'){
add();
document.getElementById("fruit").value = sumq;
}
else if(symbol == '-'){
substracte();
document.getElementById("fruit").value = sumq;
}
else if(symbol =='*'){
multiplication();
document.getElementById("fruit").value = sumq;
}
else{
division();
document.getElementById("fruit").value = sumq;
}
//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
}
<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
var req1, req2;
var sumq;
function add(req1,req2){
sumq = req1 + req2;
debugger
return sumq;
}
function substracte(req1,req2){
sumq = req1 - req2;
return sumq;
}
function multiplication(req1,req2){
sumq = req1 * req2;
return sumq;
}
function division(req1,req2){
sumq = req1 / req2;
return sumq;
}
function count(){
req1 = parseInt(document.getElementById("txt1").value);
req2 = parseInt(document.getElementById("txt2").value);
var symbol = document.getElementById("select");
var index = select.selectedIndex;
var fuhao = select.options[index].value;
if(fuhao =='+'){
var value = this.add(req1, req2);
document.getElementById("fruit").value = value;
}
else if(fuhao == '-'){
var value = this.substracte(req1,req2);
document.getElementById("fruit").value = value;
}
else if(fuhao =='*'){
var value = this.multiplication(req1,req2);
document.getElementById("fruit").value = value;
}
else{
var value = this.division(req1,req2);
document.getElementById("fruit").value = value;
}
//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>