function form() {
  var fname = document.getElementById("ifname").value;
  var email = document.getElementById("iemail").value;
  var mobile = document.getElementById("imob").value;
  var pass = document.getElementById("ipass").value;
  var namepattern = /[a-zA-Z.]/;
  var emailpattern = /(cse|eee|law)_\d{10}@lus\.ac\.bd/;
  var mobpattern = /(\+88)?-?01[3-9]\d{8}/;
  var passpattern =
    /((?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[!@#$%^&*><?()*&+_])).{8,20}/;

  //first name
  if (fname.length < 2 || fname.length > 20) {
    // alert&#40;"length must be 2-20"&#41;;
    document.getElementById("efname")[removed] = "length must be 2-20";
    return false;
  } else if (!fname.match(namepattern)) {
    // alert&#40;"invalid input"&#41;;
    document.getElementById("efname")[removed] = "invalid input";
    return false;
  } else {
    // alert&#40;"valid"&#41;;
    document.getElementById("efname")[removed] = "";
  }
  //email
  if (!email.match(emailpattern)) {
    // alert&#40;"invalid input"&#41;;
    document.getElementById("eemail")[removed] = "invalid input";
    return false;
  } else {
    // alert&#40;"valid"&#41;;
    document.getElementById("eemail")[removed] = "";
  }
  //mobile
  if (!mobile.match(mobpattern)) {
    // alert&#40;"invalid input"&#41;;
    document.getElementById("emob")[removed] = "invalid input";
    return false;
  } else {
    // alert&#40;"valid"&#41;;
    document.getElementById("emob")[removed] = "";
  }

  //password
  if (!pass.match(passpattern)) {
    // alert&#40;"invalid input"&#41;;
    document.getElementById("epass")[removed] = "invalid input";
    return false;
  } else {
    // alert&#40;"valid"&#41;;
    document.getElementById("epass")[removed] = "";
  }
}