I wanted to know how it could be printed in the following input text:
document.getElementById('btn-geo').addEventListener('click', function() {
geocodeLatLng(geocoder, map, infowindow);
document.getElementById('txt-ubicacion').value = "";
});
The following information:
infowindow.setContent(results[1].formatted_address);
which receives in text the location of a user: 
This is the code I'm working with:
$(document).ready(function(){
// the "href" attribute of .modal-trigger must specify the modal ID that wants to be triggered
$('.modal-trigger').leanModal();
$('.modalM').click()
});
var map, infoWindow, pos, marker
if ( navigator.geolocation ) {
navigator.geolocation.getCurrentPosition(function (position) {
pos = {
lat: position.coords.latitude,
lng: position.coords.longitude
}
initMap()
})
} else {
alert('Tu Navegador no soporta la Geolocalización')
}
initMap();
function initMap() {
var map = new google.maps.Map(document.getElementById('map'), {
zoom: 8,
center: {lat: 40.731, lng: -73.997}
});
var geocoder = new google.maps.Geocoder;
var infowindow = new google.maps.InfoWindow;
document.getElementById('btn-geo').addEventListener('click', function() {
geocodeLatLng(geocoder, map, infowindow);
document.getElementById('txt-ubicacion').value = "";
});
}
function geocodeLatLng(geocoder, map, infowindow) {
var input = document.getElementById('latlng').value= pos.lat + "," + pos.lng;
var latlngStr = input.split(',', 2);
var latlng = {lat: parseFloat(latlngStr[0]), lng: parseFloat(latlngStr[1])};
geocoder.geocode({'location': latlng}, function(results, status) {
if (status === google.maps.GeocoderStatus.OK) {
if (results[1]) {
map.setZoom(11);
var marker = new google.maps.Marker({
position: latlng,
map: map
});
infowindow.setContent(results[1].formatted_address);
infowindow.open(map, marker);
} else {
window.alert('No results found');
}
} else {
window.alert('Geocoder failed due to: ' + status);
}
});
}