JS验证字符串是否以某一子串结尾,验证字符串是否以某一子串开始

function endWith (value,str) {
	if (str == null || str == "" || value.length == 0 || str.length > value.length)
		return false;
	if (value.substring(value.length - str.length) == str)
		return true;
	else
		return false;
	return true;
};

function startWith (value,str) {
	if (str == null || str == "" || value.length == 0 || str.length > value.length)
		return false;
	if (value.substr(0, str.length) == str)
		return true;
	else
		return false;
	return true;
};