/**
 * 根据日期字符串获取星期几
 * @param dateString 日期字符串（如：2016-12-29），为空时为用户电脑当前日期
 * @returns {String}
 */
function getWeek(dateString){
	var date;
	if(isNull(dateString)){
		date = new Date();
	}else{
		var dateArray = dateString.split("-");
		date = new Date(dateArray[0], parseInt(dateArray[1] - 1), dateArray[2]);
	}
	//var weeks = new Array("日", "一", "二", "三", "四", "五", "六");
	//return "星期" + weeks[date.getDay()];
	return "星期" + "日一二三四五六".charAt(date.getDay());
};