Is there a way to get an xmlHttpRequest load time?
Otherwise I'll have to set a function that count it, so?
To the best of my knowledge there isn't an execution time included as part of the XMLHTTPRequest object. You can, however, use JS to calculate this value:
const start = Date.now();
// Execute request
alert( "Request took: " + ( Date.now() - start ) );
For more info on the data that is stored in the XMLHTTPRequest object, see this page.