email format very loose check

validateEmail.js

    function validateEmail(email) {
        // The real RFC complain email format check will be something look like this
        // http://ex-parrot.com/~pdw/Mail-RFC822-Address.html
        // so let's make a very loose check here to let go most cases
        
        if ( typeof email != "string" ) {
            return false;
        }

        var pstAt = email.indexOf('@');

        // @ be the first char
        if ( pstAt <= 0 ) {
            return false;
        }
        // at least 1 char before and after the dot
        else if ( pstAt > email.length - 4 ) {
            return false
        }

        var domain = email.substr( pstAt + 1, email.length );
        var pstDot = domain.indexOf('.');

        if ( domain.indexOf('@') >= 0 ) {
            // only one 'at'
            return false;
        }

        if ( pstDot <= 0 ) {
            // at least one dot behind the 'at'
            // dot should not follow 'at' immediately
            // Ps. dot at the last is allowed
            return false;
        }

        return true;
    }