@korina Hi, sorry but I don't understand how the post you suggested can help me. My code is the same as the tutorial but the error I mentioned in ther previous post occurs.
Here is my js code:
var options = {
key: '**MY KEY**',
verbose: true,
lat: 50.4,
lon: 14.3,
zoom: 5,
};
windyInit(options, function (windyAPI) {
vm.map = windyAPI;
L.popup()
.setLatLng([50.4, 14.3])
.setContent('<p>Hello world!<br />This is a nice popup.</p>')
.openOn(vm.map);
});