javascript validation for age

<script type="text/javascript">
       $(document).ready(function () {
           $("#Button1").click(function () {
               var res = document.getElementById("TextBox1").value;

               if (res<1 || res > 100)
                   alert("your message");
           })

       })
   </script>

var age=document.getElementById('ageTextBox').value;

// Convert user entered age to a number

age = parseInt(age, 10);

//check if age is a number or less than or greater than 100
if (isNaN(age) || age < 1 || age > 100)
{ 
  alert("The age must be a number between 1 and 100");
  return false;
}

First name: <input type="number" id="element_id">
<br>
<button type="button" id="Button1">Click Me!</button>

$(function () {
    $("#Button1").on("click", function () {

        if ($('#element_id').val() > 100 || $('#element_id').val() < 1) {
            alert("Please enter a number between 1 - 100 ");
        }

    });

});

<label>Enter Your Age : </label>
<input type="text" id="txtAge" onkeyup="ageValidation()">

function ageValidation() 
{
     var x = document.getElementById("txtAge").value;
     if (x < 1 || x > 100)
     {
            alert("enter age between 1 to 100")
     }
}

<label>Enter Your Age : </label>
<input type="text" id="txtAge" onkeyup="ageValidation()">

function ageValidation() 
{
     var x = document.getElementById("txtAge").value;
     if (x < 1 || x > 100)
     {
            alert("enter age between 1 to 100")
     }
}