Here is the code, what I expect now is the prompt frame to appear, but it is not, and I am asking myself where is the mistake...

Please, if someone is in the mood, can someone help?

Many thanks!

<!DOCTYPE html>

  <p>Please, input 3 numbers 1-9, separated by commas:</p>
  <input id="angle" type="array">
    <button onclick="myFunction()">Search!!!</button>
    function myFunction()
    var a=prompt("Please, input a number: ","a");
    var x=document.getElementById("pravokotnik").value;
   for (int i=0; i<5; i+=2){
   if (x[i]==a){alert("Number IS on the list!")} 

   else{alert("Number is NOT on the list!")}