You want to put a value in the input form

I want to change < p id="demo" > </ p> to < input type="text" id="demo" >

<button onclick="getLocation()">Try It</button>

<p id="demo"></p>

<script>
var x = document.getElementById("demo");

function getLocation() {
  if (navigator.geolocation) {
    navigator.geolocation.getCurrentPosition(showPosition);
  } else { 
    x.innerHTML = "Geolocation is not supported by this browser.";
  }
}

function showPosition(position) {
  x.innerHTML = "Latitude: " + position.coords.latitude + 
  "<br>Longitude: " + position.coords.longitude;
}
</script>

demo"> to < input type="text" id="demo">

>Solution :

if i understood your questions correctly, maybe something like this?

<button onclick="getLocation()">Try It</button>

<input type="text" id="demo" />

<script>
var x = document.getElementById("demo");

function getLocation() {
  if (navigator.geolocation) {
    navigator.geolocation.getCurrentPosition(showPosition);
  } else { 
    alert("Geolocation is not supported by this browser.");
  }
}

function showPosition(position) {
  x.value = position.coords.latitude + "," + position.coords.longitude;
}
</script>