Tryit Editor v2.9

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<!DOCTYPE html>
<html>
<body>

<p>The toString() method can output numbers as base 16 (hex), base 8 (octal), or base 2 (binary).</p>

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

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

<script>
function myFunction() {
    var myNumber = 128;
    document.getElementById("demo").innerHTML = "128 = " + 
    myNumber + " Decimal, " +
    myNumber.toString(16) + " Hexadecimal, " +
    myNumber.toString(8) + " Octal, " +
    myNumber.toString(2) + " Binary."
}
</script>

</body>
</html>