How to get username from authentication prompt popup

Question

I have SharePoint Online classic page which has some custom JavaScript and jQuery scripts implemented and third party .NET app requiring some basic auth. When the user visits the page he is prompted to enter username and password. How can I get the username from this prompt? Prompt is standard and looks like this (picture is not mine)

Answer 1

You can use SharePoint's javascript API to retrieve the current user's information.

_spPageContextInfo.userId

see: https://social.technet.microsoft.com/wiki/contents/articles/29766.sharepoint-understanding-the-sppagecontextinfo-object.aspx

Another suggestion is to use the API:

<script type="text/javascript">
ExecuteOrDelayUntilScriptLoaded(getCurrentUser, "sp.js");
 
var currentUser;
 
function getCurrentUser(){
var ctx= new SP.ClientContext.get_current();
var web = ctx.get_web();
currentUser = web.get_currentUser();
ctx.load(currentUser);
ctx.executeQueryAsync(onSuccess, onFailure);
}
 
function onSuccess() {
alert(currentUser.get_title()); // Domain\Account 
alert(currentUser.get_email());
document.getElementById('userLogin').innerHTML = currentUser.get_loginName(); 
}
 
function onFailure() {
alert('request failed' + args.get_message() + '\n' + args.get_stackTrace());
}
 
</script>
 
<div>Currently Logged User:
    <span id="userLogin"></span>
</div>

MS reference: https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/complete-basic-operations-using-sharepoint-client-library-code

Answer 2

If someone is still interested in this I found a way to get the user principal name with microsoft graph API https://docs.microsoft.com/en-us/graph/api/user-get?view=graph-rest-1.0&tabs=http

https://graph.microsoft.com/v1.0/me?$select=mailnickname,onpremisesUserprincipalName was the actual request I needed