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in my code, i got some buttons as < 1 2 3 >.
after i click the above buttons, some times it pop up a window
with undifine, some times it pop up a window with the right value. This is my code's problem, could any one help me to solve this problem, please.
index.html
<html>
<body><input type="button" id="b<" name="bb<" value="<" onClick="cButtons()">
<input type="button" id="b1" name="bb1" value="1" onClick="cButtons()">
<input type="button" id="b2" name="bb2" value="2" onClick="cButtons()">
<input type="button" id="b3" name="bb3" value="3" onClick="cButtons()">
<input type="button" id="b>" name="bb>" value=">" onClick="cButtons()">
<script type="text/javascript">
var rValue;
function cButtons(){
ajaxFunction();
alert(rValue);
}
function ajaxFunction()
{
var xmlHttp;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
// Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e)
{
alert("Your browser does not support AJAX!");
return false;
}
}
}
xmlHttp.onreadystatechange=function()
{
if(xmlHttp.readyState==4)
{
rValue=xmlHttp.responseText;
}
}
xmlHttp.open("GET","cateV.php",true);
xmlHttp.send(null);
}
</script>
</body>
</html>
cateV.php
<?php
$test="i am testing";
echo $test;
?>
xmlHttp.onreadystatechange=function()
{
if(xmlHttp.readyState==4)
{
rValue=xmlHttp.responseText;}
}
xmlHttp.open("GET","cateV.php",true);
xmlHttp.send(null);
xmlHttp.open("GET","cateV.php",false);
xmlHttp.send(null);
rValue=xmlHttp.responseText;
Untested, but should work
xmlHttp.open("GET","cateV.php",false);//set a synchronous request.
xmlHttp.send(null); //All scripting on the page will now stop until cateV.php is got
rValue=xmlHttp.responseText;//set the text as your value. Seeing as we know we have the page there is no need to use onreadystatechange
1)
xmlHttp.onreadystatechange=function()
{
if(xmlHttp.readyState==4)
{
rValue=xmlHttp.responseText;}
}
The above means the browser send requests to server one by one, and it receives data from server also one by one, Am I right?
rValue=xmlHttp.responseText;
without the xmlHttp.onreadystatechange=function(), does it means the browser can send many requests to server at the same time, and it also
can receive many data from server at the same time as well.
2)
xmlHttp.open("GET","cateV.php",false);
xmlHttp.send(null);
rValue=xmlHttp.responseText;
why you put the "rValue=xmlHttp.responseText;" in the last position, not on the top of them?
