how to stay on same page after alert in JavaScript

Question

onClick=validateForm() it shows alert if it is blank but it goes to next page("action=some.php") so any idea how to be on same page after alert?

function validateForm() {    
  var x = document.forms["uploadForm"]["userImage"].value;    
  if (x == "") {           
    alert("Choose the file !!!!!");
    return false;
  }
  var p = document.forms["uploadForm"]["Start_Date"].value;
  var q = document.forms["uploadForm"]["End_Date"].value;
  if (p == "" && q=="") {
    alert("Select the date !!!!!");
    return false;   
  }
  var radio = document.forms["uploadForm"]["radio"].value;
  if (radio == "") {
    alert("Select the Radio !!!!!");
    return false;
  }     
}

Answer 1

I used onClick="return validateForm()" in place of onClick=validateForm() . Thank you so much @epascarello for your quick answer.