简单计算机的编写,该怎么解决 _JavaScript

简单计算机的编写

<body>
<form id="form1" name="form1" method="post" action="">
<label>
<input type="text" name="text1" id="text1"/>
<select name="select" id="select">
<option value="add">+</option>
<option value="minus">-</option>
<option value="multiply">*</option>
<option value="divide">/</option></select>
<input type="text" name="text2" id="text2"/>
<input name="equel" type="button" id="equel" onclick="count()" value="="/>
<input type="text" name="text3" id="text3"/>
</label>
</form>
</body>
</html>
<script language="javascript">
function count()
{
var text1 = document.getElementById("text1");
var text2 = document.getElementById("text2");
var text3 = document.getElementById("text3");
var mark = document.getElementById("select").value;
if(mark == "add")
text3 = parseInt(text1) + parseInt(text2) ;
if(mark == "minus")
text3 = parseInt(text1) - parseInt(text2) ;
if(mark == "multiply")
text3 = parseInt(text1) * parseInt(text2) ;
if(mark == "divide")
text3 = parseInt(text1) / parseInt(text2) ;

}
</script>

大家帮忙看下为什么那个调用“count()”这个函数没有反应呢

------解决方案--------------------
text3.value = ...
------解决方案--------------------
text1 = document.getElementById("text1").value;
text3.value = ...

------解决方案--------------------

HTML code

<html>
<head>
    
    </head>
    <body>
<form id="form1" name="form1" method="post" action="">
 
  <input type="text" name="text1" id="text1"/>
  <select name="select" id="select">
  <option value="add">+</option>
  <option value="minus">-</option>
  <option value="multiply">*</option>
  <option value="divide">/</option></select>
  <input type="text" name="text2" id="text2"/>
  <input name="equel" type="button" id="equel" onclick="count()" value="="/>
  <input type="text" name="text3" id="text3"/>

</form>
</body>
</html>
<script language="javascript">
function count()
{
var text1 = document.getElementById("text1").value;
var text2 = document.getElementById("text2").value;
var text3 = document.getElementById("text3");
  var mark = document.getElementById("select").value;
  if(mark == "add")
  text3.value = parseInt(text1) + parseInt(text2) ;
  if(mark == "minus")
  text3.value = parseInt(text1) - parseInt(text2) ;
  if(mark == "multiply")
  text3.value= parseInt(text1) * parseInt(text2) ;
  if(mark == "divide")
  text3.value= parseInt(text1) / parseInt(text2) ;

}
</script>
    </body>
<html>