function checkvalid()
{
	if(validate() == true)
	{
		document.frmfriend.submit();
	}
}

function validate()
{
	var friendname = document.frmfriend.txtfriendname.value;
	var name = document.frmfriend.txtname.value;
	
	if(ltrim(friendname).length < 1)
	{
		alert("Please enter your friend's name");
		document.frmfriend.txtfriendname.focus();
		return false;
	}
	
	if(ltrim(name).length < 1)
	{
		alert("Please enter your name");
		document.frmfriend.txtname.focus();
		return false;
	}
	
	var frndsurname = document.frmfriend.txtfrndsurname.value;
	var surname = document.frmfriend.txtsurname.value;
	
	if(ltrim(frndsurname).length < 1)
	{
		alert("Please enter your friend's surname");
		document.frmfriend.txtfrndsurname.focus();
		return false;
	}
	
	if(ltrim(surname).length < 1)
	{
		alert("Please enter your surname");
		document.frmfriend.txtsurname.focus();
		return false;
	}
	
	var frndemail = document.frmfriend.txtfrndemail.value;
	var email = document.frmfriend.txtemail.value;
	
	if(isvalid_email(frndemail) == false)
	{
		alert("Please check your friend's email");
		document.frmfriend.txtfrndemail.focus();
		return false;
	}
	
	if(isvalid_email(email) == false)
	{
		alert("Please check your email");
		document.frmfriend.txtemail.focus();
		return false;
	}
	
	var frndaddress = document.frmfriend.txtfrndaddress.value;
	var address = document.frmfriend.txtaddress.value;
	
	if(ltrim(frndaddress).length < 1)
	{
		alert("Please enter your friend's address");
		document.frmfriend.txtfrndaddress.focus();
		return false;
	}
	
	if(ltrim(address).length < 1)
	{
		alert("Please enter your address");
		document.frmfriend.txtaddress.focus();
		return false;
	}
	
	var frndtelno = document.frmfriend.txtfrndtelno.value;
	var telno = document.frmfriend.txttelno.value;
	
	if(ltrim(frndtelno) < 1)
	{
		alert("Please enter your friend's telephone number");
		document.frmfriend.txtfrndtelno.focus();
		return false;
	}
	
	if(isvalid_telno(frndtelno) == false)
	{
		alert("Please check your friend's telephone number");
		document.frmfriend.txtfrndtelno.focus();
		return false;
	}
	
	if(ltrim(telno).length < 1)
	{
		alert("Please enter your telephone number");
		document.frmfriend.txttelno.focus();
		return false;
	}	
	
	if(isvalid_telno(telno) == false)
	{
		alert("Please check your telephone number");
		document.frmfriend.txtfrndtelno.focus();
		return false;
	}
	
	var frndtime = document.frmfriend.txtfrndtime.value;
	var yourtime = document.frmfriend.txttime.value;
	
	if(ltrim(frndtime).length < 1)
	{
		alert("Please enter your friend's preference of telephone call time");
		document.frmfriend.txtfrndtime.focus();
		return false;
	}	
	
	if(ltrim(yourtime).length < 1)
	{
		alert("Please enter your preference of telephone call time");
		document.frmfriend.txttime.focus();
		return false;
	}	
	return true;
}

function ltrim(str)
{
	var i;
	var newstr = "";
	var char;
	var flag = 0;

	for(i=0;i<str.length;i++)
	{
		char = str.charAt(i);
		if(char >= 'a' && char <= 'z')
		{
			newstr = newstr.concat(char);
			flag = 1;
		}
		if(char >= 'A' && char <= 'Z')
		{
			newstr = newstr.concat(char);
			flag = 1;
		}
		if(char >= '0' && char <= '9')
		{
			newstr = newstr.concat(char);
			flag = 1;
		}	
		if(flag == 1)
		{
			if(char == ' ' || char == "-" || char == '-')
			{
				newstr = newstr.concat(char);
			}
		}
	}
	return newstr;
}	 

var emailfilter=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i;

function isvalid_email(str)
{
	return emailfilter.test(str);
}

function isvalid_telno(str)
{
	if(isNaN(Number(str)) == true)
	{
		return false;
	}
	else
	{
		return true;
	}
}