email javascript

var vemail="Email must be a valid Email address (like companyname@yahoo.com).";var vzipcode=" must be a 6 or 5 (for US Country) digit Pin Code (eg: '600012' or '12345')";var vempty=" should not be blank";var whitespace = " \t\n\r";var vnum=" should be a number";var vRange = " should greater than ";
function checkNull(s,f){//To check Null values if (isWhitespace(s.value)) return warnInvalid (s,f,vempty); else return true;}
function checkCmb(s,f){//To check Null values
if (s.value != "-1") { return true; } else{ s.focus(); alert(f +vempty);return false; } }function isWhitespace(s){ //To check whitespaces var i; if ((s == null) (s.length == 0)) return true; for (i = 0; i < s.length; i++){ var c = s.charAt(i); if (whitespace.indexOf(c) == -1) return false; } return true;}
function warnInvalid(theField, s,errmsg){//Error message theField.focus(); theField.select(); alert(s +errmsg); return false;}
function checkEmail (s,f,t){//To check Email if (t == "r"){ if (checkNull(s,f)){ if (isEmail(s.value)){ return true; } else{ f=""; return warnInvalid (s,f, vemail); } } else return false; } else{ if (s.value != ""){ if (isEmail(s.value)){ return true; } else{ f=""; return warnInvalid (s,f, vemail); } } else return true; } }
function isEmail (s){ if ((s == null) (s.length == 0)) if (isEmail.arguments.length == 1) return false; else return (isEmail.arguments[1] == true); if (isWhitespace(s)) return false; var i = 1; var sLength = s.length; while ((i <>= sLength) (s.charAt(i) != "@")) return false; else i += 2; while ((i <>= sLength - 1) (s.charAt(i) != ".")) return false; else return true;}
function checkNumber(s,f,t){//To check Number if (t == "r"){ if (checkNull(s,f)){ if (!isInteger(s.value)){ return warnInvalid(s,f,vnum); } else return true; } else return false; } else{ if (s.value != ""){ if (!isInteger(s.value)){ return warnInvalid(s,f,vnum); } else return true; } else return true; } }
function checkValidNumber(s,f,t){//To check Number if(s.value +0 < t ) { return warnInvalid(s,f,vRange + (t-1) ); } else return true; }
function isInteger (s){ var i; if ((s == null) (s.length == 0)) if (isInteger.arguments.length == 1) return false; else return (isInteger.arguments[1] == true); for (i = 0; i < s.length; i++){ var c = s.charAt(i); if (!isDigit(c)) return false; } return true;}
function checkZipcode(s,f,t){//To check Zipcodeif (t == "r"){ if (s.value.length == 5 s.value.length == 6){
return checkNumber(s,f,t);
} else return warnInvalid (s,f,vzipcode); }else{ if (s.value != ""){ if (s.value.length == 5 s.value.length == 6){
return checkNumber(s,f,t);
} else return warnInvalid (s,f,vzipcode); } else return true; }}
function isDigit (c){ return ((c >= "0") && (c <= "9"));}