var dataArray = [];
    var regExp = new RegExp(/(\d{4})(\d{2})(\d{2})/);
	    var weekTime = dojo.map(data,function(item,index){
			regExp.test(item.exchange_date);
			return RegExp.$1 + "-" +  RegExp.$2 + "-" + RegExp.$3;
		});
	    console.log(weekTime);