you must use some server-side code anyway, because JS doesn't allow to upload file and even access it on users computer
so you can not get the contents of this file if not uploading it to server (upd: actually you can do it, so this is only a suggestion)
but you can do it in very simple way e.g. submit a form with file input
<form enctype="multipart/form-data" action="/path/to/script" method="post">
<input name="myFile" type="file" />
</form>
to send it using ajax and get the contents of it as a response from the easy script like this:
<?php
if (!$_FILES["myFile"]["error"]) {
header("Content-Type: text/xml");
echo file_get_contents($_FILES["myFile"]["tmp_name"]);
}
?>
I'm using php, but I'm sure it's not a problem to perform it in another language. Of course I know that file uploading is supported only by XHR2 in major browsers, but as far as you are asking about HTML5 this solution will work.
Next step is to add success handler to your ajax request
success: function(data) {
// and parse it
if (window.DOMParser)
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(data,"text/xml");
}
else // Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.loadXML(data);
}
}
Great tutorial here. Now you can access xml contents using xmlDoc var like simple DOM document.