JavaScript phone number Fax number legality verification code

if ((document.regform.u_telphone1.value.length==0) | |! Checkifnumber (Document.regform.u_telphone1.value)) {
Alert ("Hint: the phone must be filled out!") ");
Document.regform.u_telphone1.focus ();
return false;
}
if ((document.regform.u_telphone2.value.length==0) | |! Checkifnumber (Document.regform.u_telphone2.value)) {
Alert ("Hint: the phone must be filled out!") ");
Document.regform.u_telphone2.focus ();
return false;
}
if ((document.regform.u_telphone3.value.length==0) | |! Checkifnumber (Document.regform.u_telphone3.value)) {
Alert ("Hint: the phone must be filled out!") ");
Document.regform.u_telphone3.focus ();
return false;
}

Mobile phone Number verification code

if (document.regform.u_mobile.value.length!=0) {
if (!checkifnumber (Document.regform.u_mobile.value)) {
Alert ("Hint: Phone number format is wrong!") ");
Document.regform.u_mobile.focus ();
return false;
}
if (Document.regform.u_mobile.value.charat (0)!= "1") {
Alert ("Hint: Phone number format is wrong!") ");
Document.regform.u_mobile.focus ();
return false;
}
if (document.regform.u_mobile.value.length!=11) {
Alert ("Hint: Phone number format is wrong!") ");
Document.regform.u_mobile.focus ();
return false;
}

}

Fax Facsimile number verification

  if (document.regform.u_fax.value.length!=0) {
  if (!checkiffax (document.regform.u _fax.value)) {
                Alert ("Hint: fax number is malformed!") ");
    document.regform.u_fax.focus ();
                return false;
  }
    }