JSFiddle - React, Tailwind, and code Playground

HTML

<input id="textbx" type="text" /><button id="btn" disabled="disabled">go</button>
 <span id="msg"></span>

CSS

#msg
{
color: red;
}

JavaScript

$("#textbx").keyup(function(){
 if ($("#textbx").val().length > 0) {
	  $("#btn").removeAttr('disabled');
 
   }
});


 
 
 
  $("#btn").click(function(){
						  
   var num =parseInt($("#textbx").val()); 
   
        if(isPrime(num))
		{
            $("#msg").html("yupp").show().fadeOut("slow");
		}
		else
		{
            $("#msg").html("huh").show().fadeOut("slow");
		}
  });

function isPrime(n) {

   // If n is less than 2 or not an integer then by definition cannot be prime.
   if (n < 2) {return false}
   if (n != Math.round(n)) {return false}

   // Now assume that n is prime, we will try to prove that it is not.
   var isPrime = true;

   // Now check every whole number from 2 to the square root of n. If any of these divides n exactly, n cannot be prime.
   for (var i = 2; i <= Math.sqrt(n); i++) {
      if (n % i == 0) {isPrime = false}
   }

   // Finally return whether n is prime or not.
   return isPrime;

}