This should complain if the input is not valid XML or valid KML

[tmcw]

Options:

• Look for the kml tag, if it is not found, return an error.

[Raruto]

Here are a few lines useful to achieve this:

if (data.indexOf("<") != 0) {
  throw 'Invalid XML';
}

let xml  = (new DOMParser()).parseFromString(data, "text/xml");

let type = xml.documentElement.tagName.toLowerCase(); // "kml" or "gpx"

if (xml.getElementsByTagName('parsererror').length) {
  throw 'Invalid XML';
}

Source: leaflet-elevation/src/control.js#L956-L975

👋 Raruto