function substringBetween( str,  open,  close)
{
        if(str == null || open == null || close == null)
            return null;
        start = str.indexOf(open);
        if(start != -1)
        {
            end = str.indexOf(close, start + open.length);
            if(end != -1)
                return str.substring(start + open.length, end);
        }
        return null;
}

function substringBefore(str, separator)
{
        if(str == null || separator == null || str.length == 0)
            return str;
        if(separator.length == 0)
            return "";
        pos = str.indexOf(separator);
        if(pos == -1)
            return str;
        else
            return str.substring(0, pos);
}


function trimLeft(str) {
	var rtnStr = "";
	for (var i = 0; i < str.length; i++){
	if (str.charAt(i) != " "){
	rtnStr = str.substr(i);
	break;
	}
	}
	return rtnStr;
}

/*
 * 去除字符串右边的空格
 * @str 待处理字符串
 * @return 去除右边空格的字符串
 */
function trimRight(str) {
	var rtnStr = "";
	for (var i = str.length - 1; i >= 0; i--){
	if (str.charAt(i) != " "){
	rtnStr = str.substring(0, i + 1);
	break;
	}
	}
	return rtnStr;
}

/*
 * 去除字符串左右边的空格
 * @str 待处理字符串
 * @return 去除左右边空格的字符串
 */
function trim(str) {
	str = trimLeft(str);
	str = trimRight(str);
	return str;
}

function getSubStrTotal(inputString, subString) {
	var total = 0;
	if (trim(inputString) == "") {
		return 0;
	} 

	while (inputString.indexOf(subString) != -1) {
		inputString = inputString.replace(subString, "");
		total += 1;
	}
	return total;
}

function isInputEmail(texto) {

	var tvalue = trim(texto.value); // email
	texto.value = tvalue;

	if (tvalue == "") { // email值为空时,返回true
		return true;
	}
	
	if (getSubStrTotal(tvalue, "@") == 1
		&& getSubStrTotal(tvalue, ".") >= 1 
		&& getSubStrTotal(tvalue, "@.") != 1 
		&& getSubStrTotal(tvalue, ".@") != 1) {
		return true;
	}
	else {
		alert("E-mail address invalid, please try again.");
		texto.focus();
		return false;
	}
}