<!DOCTYPE html>
<html>
<body>
Search: <input type="search" id="mySearch" maxlength="30">
<p>Click the button to display the value of the maxlength attribute of the search field.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var x = document.getElementById("mySearch").maxLength;
document.getElementById("demo").innerHTML=x;
}
</script>
</body>
</html>