I am using a asp.net MVC4 web application ,in which I need to install a software from ftp if the client machine not already installed it. During installation writing some data to the registry of the client machine , like:
Test
|__DefaultIcon
|__Shell
|__Open
|__command
Where in Test write something like below in registry.
This entry will occur only after installing the software.So I can automatically initialise the software next time somebody try to download it,machine already have the software. To initialise the software using the below code:
<script type="text/javascript">
function LaunchURLScript() {
var url = "Test:";
// Creates an object which can read files from the server
var reader = new XMLHttpRequest();
// Opens the file and specifies the method (get)
// Asynchronous is true
reader.open('GET', url, true);
//check each time the ready state changes
//to see if the object is ready
reader.onreadystatechange = checkReadyState;
function checkReadyState() {
if (reader.readyState === 4) {
//check to see whether request for the file failed or succeeded
if ((reader.status == 200) || (reader.status == 0)) {
//page exists -- redirect to the checked
//checked for page
// document.location.href = url;
window.open(url);
self.focus();
}
else {
alert("456");
//does nothing and quits the function
//if the url does not exist
return;
}
}//end of if (reader.readyState === 4)
}
// end of checkReadyState()
// Sends the request for the file data to the server
// Use null for "get" mode
try{
reader.send(null);
}
catch (err) {
alert(err.message);
}
}
</script>
But the problem is window.open(url) will exicute evenif the url not exist,which means software not installed.Please help to find out whether the url exist or not before calling window.open(url)
