Using XMLHttpRequest To Paste Clipboard - python-3.x

Question

I am currently using Flask to create a website and have come across an interesting issue. There is some code that gives the user the option to input a value in for about 20 separate input fields. What I am trying to do is construct a button that would allow the user to paste in a column from an Excel table. Essentially, a button that will look at the clipboard, take the field, convert the string into an array, and place the values into each input in the order they appear in the list.
So far, I have been able to get the clipboard into a string using tk.Tk().clipboard_get(), and believe that I can get this value by making an XMLHttpRequest, but have had little luck in making it actually work.
Some code for what I am trying to accomplish:
Python:
#app.route('/some/path/here', methods = ['GET'])
def paste():
try:
values = tk.Tk().clipboard_get()
values = values.replace('\n',',')
return values
except:
return None
HTTP:
<button type="button" style="float: right" onclick="Testing()">Paste</button>
<p id="textHere"></p>
JavaScript:
<script>
function Testing() {
var wvpst = new XMLHttpRequest();
wvpst.onreadystatechange = function(){
if (this.readyState == 4 && this.status == 200) {
var list = this.responseXML;
// list = list.replace(/'/g,"").replace(/ '/g,"");
// list = list.split(", ");
document.getElementById("textHere").innerHTML = list;
}
}
wvpst.open("GET","{{ url_for('paste') }}",true);
wvpst.send();
}
</script>
For now, I am just trying to get the list of values copied from an Excel sheet, but nothing is being returned when the button is pressed. Am I simply using XMLHttpRequest incorrectly or is there something else I need to do to get this to work?

Answer 1

Set a debug breakpoint inside
if (this.readyState == 4 && this.status == 200) {
}
and inspect your response. Set another on the first line of your function in Flask. Those should give you visibility into where the breakdown is.
A few other, perhaps more important notes:
Point 1) In your flask try/except, on failure you should serve a response, just a 500 response. Replace return None with:
return app.make_response('Couldn't parse clipboard information!'), 500
Point 2) There is no need to pass this information to your server for processing. You can accomplish this within the javascript of the front end and save your server some processing and your client some time waiting on an HTTP response.
Have the user paste their content into a textbox or another element, and then access the value from there.
Direct clipboard access isn't something most browsers give up freely, and so best to avoid that route.
Summary:
Your xmlhttprequest looks fine to me. I would guess that your try in flask is failing and returning something useless if anything at all.
Do this in javascript.