function jtrim(str)
{	 while (str.charAt(0)==" ")
	 	 {str=str.substr(1);}	  
	 while (str.charAt(str.length-1)==" ")
		 {str=str.substr(0,str.length-1);}
	 return(str);
}

function CheckEmpty(Field, FieldTitle)
	{
		if (jtrim(Field.value) == "")
		{
			alert("Please fill in \"" + FieldTitle + "\"");
			Field.focus();
			return false;
		}
		
		return true;
	}
	
	
function CheckInteger(Field, FieldTitle)
	{Field.value=jtrim(Field.value);
		if (Field.value != "")
		{
			for (i = 0; i < Field.value.length; i++)
			{
				ch = Field.value.charAt(i);
				
				if ( (ch < '0' || ch > '9') && ch != '-' ) {
					alert("\"" + FieldTitle + "\" only numbers are allowed.");
					Field.focus();
					return	false;
				}
			}
		}
		
		return true;
	}
	
function CheckReal(Field, FieldTitle)
	{
		if (Field.value != "")
		{
			DotNum = 0;
			for (i = 0; i < Field.value.length;  i++)
			{
				ch = Field.value.charAt(i);
				
				if ((ch < '0' || ch > '9') && ch != '.') 
				{
					alert("\"" + FieldTitle + "\"  only numbers are allowed.");
					Field.focus();
					return false;
				}
				
				if (ch == '.')
				{
					if (DotNum > 0) 
					{
						alert("\"" + FieldTitle + "\"  only one radix point is allowed.");
						Field.focus();
						DotNum++;
						return false;
					}
				}
			}
		}
		
		return	true;
	}

	
function CheckOption(Field, FieldTitle) 
	{
		for (i = 0; i < Field.length; i++)
			if (Field[i].checked)
				return true;
				
		alert("Please select \"" + FieldTitle + "\".");
		return false;
	}

	//此函数用于判断Email地址是否正确
function CheckEmail(Field)
{

   // there must be >= 1 character before @, so we
   // start looking at character position 1
   // (i.e. second character)
   var i = 1;
   var len = Field.value.length;

	if (len > 50)
	{
		window.alert("Email address only less than 50 is allowed!");
		Field.focus();
		return false;
	}
	
	pos1 = Field.value.indexOf("@");
	pos2 = Field.value.indexOf(".");
	pos3 = Field.value.lastIndexOf("@");
	pos4 = Field.value.lastIndexOf(".");
	//check '@' and '.' is not first or last character
	if ((pos1 <= 0)||(pos1 == len-1)||(pos2 <= 0)||(pos2 == len-1))  
	{
		window.alert("Email is not valid!");
		Field.focus();
		return false;
	}
	else
	{
		//check @. or .@
		if( (pos1 == pos2 - 1) || (pos1 == pos2 + 1) 
		  || ( pos1 != pos3 )  //find two @
		  || ( pos4 < pos3 ) ) //. should behind the '@'  		
		{
			window.alert("Email is not valid!");
			Field.focus();
			return false;
		}
	}
	return true;
}

	function CheckMaxLength(Field, MaxLength, FieldTitle)
	{
		if (Field.value != "")
		{
			if (Field.value.length > MaxLength)
			{
				alert("Less than " + MaxLength + " characters in \""+ FieldTitle + "\" is valid.");
				Field.focus();
				return false;
			}
		}
		
		return true;
	}
	
	function CheckMinLength(Field, MinLength, FieldTitle)
	{
		if (Field.value != "")
		{
			if (Field.value.length < MinLength)
			{
				alert("At least " + MinLength + " characters in \""+ FieldTitle + "\" is valid.");
				Field.focus();
				return false;
			}
		}
		
		return true;
	}
	
	function CheckMustLength(Field, MustLength, FieldTitle)
	{
		if (Field.value != "")
		{
			if (Field.value.length != MustLength)
			{
				alert("\"" + FieldTitle + "\" must be " + MustLength + " characters.");
				Field.focus();
				return false;
			}
		}
		
		return true;
	}
	
	function CheckMaxValue(Field, MaxValue, FieldTitle)
	{
		if (Field.value != "")
		{
			if (Field.value > MaxValue)
			{
				alert("It must be no bigger than " + MaxValue + " in \"" + FieldTitle + "\"");
				Field.focus();
				return false;
			}
		}
		
		return true;
	}
	
	function CheckMinValue(Field, MinValue, FieldTitle)
	{
		if (Field.value != "")
		{
			if (Field.value < MinValue)
			{
				alert("It must be no less than " + MinValue + " in \"" + FieldTitle + "\"");
				Field.focus();
				return false;
			}
		}
		
		return true;
	}
	
function CheckIntRange(field,prompt,min,max) {
	if ( ! CheckInteger(field,prompt) )
		return	false;
	ival = parseInt(field.value);
	if ( ival < min || ival > max ) {
		alert(prompt + "only from  " + min + " to " + max + " are allowed numbers");
		field.focus();
		return	false;
	}
	return	true;
}

function CheckRange(field1,field2,Min,Max,Prompt)
{
	if(Min > 0)
	{
		if(eval(field1.value) < Min)
		{
			alert(Prompt + " Must no less than " + Min);
			field1.focus();
			return false;
		}
		if(eval(field2.value) < Min)
		{
			alert(Prompt + " Must no less than " + Min);
			field2.focus();
			return false;
		}
	}
	if(Max > 0 && Max > Min)
	{
		if(eval(field1.value) > Max)
		{
			alert(Prompt + " Must no bigger than " + Max);
			field1.focus();
			return false;
		}
		if(eval(field2.value) > Max)
		{
			alert(Prompt + " Must no bigger than " + Max);
			field2.focus();
			return false;
		}
	}		
	if((eval(field1.value) > eval(field2.value)) || (eval(field1.value) == eval(field2.value)) )
	{
		alert(Prompt + "的上限必须大于下限");
		field1.focus();
		return false;
	}
	return true;
}