Regular expressions for JS form data verification (commonly used)

checkUserNameflag=false; 
 checkPasswordflag=false; 
 checkPasswordAgianflag=false; 
 checkEmailflag=false; 
// Username verificationfunction checkUserName() { 
 var username = $("userNeme").value; 
 var zz = /^[A-Za-z0-9]{6,}$/; 
 if (!(username)) { 
  $("userName_warn").innerHTML = "× The username does not meet the specifications"; 
  checkUserNameflag=false; 
 } else { 
  /*$("userName_warn").='blue';
   $("userName_warn").innerHTML = "√ Username is available";*/ 
  showUserExist(username); 
  checkUserNameflag=true; 
 } 
} 
//Reset promptfunction resetWarn(){ 
 $("userName_warn").innerHTML=""; 
 $("email_warn").innerHTML=""; 
 $("password_warn").innerHTML=""; 
 $("Repassword_warn").innerHTML=""; 
} 
// Password verificationfunction checkPassword() { 
 var password1 = $("password").value; 
 if ( >= 6 &&  <= 15) { 
  checkPasswordflag = true; 
  $("password_warn").='blue'; 
  $("password_warn").innerHTML = " √ Password available "; 
  checkAgianMiMa(); 
 } else { 
  checkPasswordflag = false; 
  $("password_warn").innerHTML = " × Password is at least 6 characters "; 
 } 
} 
function checkPasswordAgian() { 
 var password1 = $("password").value; 
 var password2 = $("rePassword").value; 
 if (password1 == password2) { 
  if (password1 == "") { 
   $("Repassword_warn").innerHTML = " × Please enter your password "; 
   checkPasswordAgianflag = false; 
   return; 
  } 
  $("Repassword_warn").='blue'; 
  $("Repassword_warn").innerHTML = "√ Repeat password correctly"; 
  checkPasswordAgianflag = true; 
 } else { 
  checkPasswordAgianflag = false; 
  $("Repassword_warn").innerHTML = " × The password input is different twice "; 
 } 
} 
function checkEmail(){ 
 //Verification of email  var myreg = /^([a-zA-Z0-9]+[_|\_|\.]?)*[a-zA-Z0-9]+@([a-zA-Z0-9]+[_|\_|\.]?)*[a-zA-Z0-9]+\.[a-zA-Z]{2,3}$/; 
  var email=$("email").value; 
  if(!(email)){ 
   checkEmailflag=false; 
    $("email_warn").='red'; 
   $("email_warn").innerHTML = "× The email format does not comply with the specifications"; 
  } else { 
   checkEmailflag=true; 
   $("email_warn").='blue'; 
   $("email_warn").innerHTML = "√ The email address is correct"; 
  } 
} 
function submitCheck(){ 
 alert(checkUserNameflag); 
 if(checkUserNameflag==false || checkPasswordflag==false || checkPasswordflag==false 
   ||checkPasswordAgianflag==false || checkEmailflag==false){ 
  return; 
 } 
} 
function $(id){ 
 return (id); 
}