function string_ltrim() 
{
	var str = this.replace(/(\s*)(.*)/g, "$2");
	return str;
}

function string_rtrim() 
{
	var str = this.reverse();
	var str = str.ltrim();
	var str = str.reverse();
	return str;
}

function string_trim() 
{
	var str = this.rtrim().ltrim();
	return str;
}

function string_reverse() {
	var str = "";
	for(var i=this.length-1;i>=0;i--) {
		str = str + this.substr(i, 1);
	}
	return str;
}

function string_isBlank()
{
	var str = this.trim();
	if(str.length>0)
	{
		return false;
	}
	else
	{
		return true;
	}
}

function string_isNumber()
{
	var str = this.trim();
	var found;
	for(var i=0;i<str.length;i++)
	{
		var c = str.substr(i,1);
		if(c=="0"||c=="1"||c=="2"||c=="3"||c=="4"||c=="5"||c=="6"||c=="7"||c=="8"||c=="9")
			found = false;
		else
			found = true;		
		
		if(found)
			return false;
	}
	return true;
}

String.prototype.ltrim = string_ltrim;
String.prototype.rtrim = string_rtrim;
String.prototype.trim = string_trim;
String.prototype.reverse = string_reverse;
String.prototype.isBlank = string_isBlank;
String.prototype.isNumber = string_isNumber;