How do I get the result, the comparison is bigger and smaller

Question

I want to adjust the video quality according to the dimensions when given a certain value

<input id="age" value="500" />

<button onclick="myFunction()">Try it</button>

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

<script>
function myFunction() {
  var age,en, voteable;
  age = document.getElementById("age").value;
  voteable = (720 > age < 1080 ) ? "SD":"HD":"FHD";
  document.getElementById("demo").innerHTML = " Quality:" + voteable  ;
}
</script>

Answer 1

try this!

    <input id="age" value="500" />

<button onclick="test()">Try it</button>

<p id="demo"></p>
<script>
    function test() {
        var age = document.getElementById("age").value;
        if (1080<=age) {
        document.getElementById("demo").innerHTML = "Quality: FHD";
        }
        else if (720<=age) {
        document.getElementById("demo").innerHTML = "Quality: HD";
        }
        else if (age<720) {
            document.getElementById("demo").innerHTML = "Quality: SD";
        }
    }
    </script>