字符串转时间

//匹配时间格式：20190322T142523910（严格匹配）
var DATE_REGEXP = new RegExp("^(\\d{4})(\\d{2})(\\d{2})([T\\s](\\d{2})(\\d{2})(\\d{2})(\\d{3}))$");   
 
function toDate(dateString) {       
    if (DATE_REGEXP.test(dateString)) {           
        var timestamp = dateString.replace(DATE_REGEXP, function($all, $year, $month, $day, $part1, $hour, $minute, $second, $part2, $milliscond) {               
            var date = new Date($year, $month - 1, $day, $hour || "00", $minute || "00", $second || "00", $milliscond || "00");               
            return date.getTime();           
        });           
        var date = new Date();           
        date.setTime(timestamp);    

　　　　　var year = date.getFullYear();
　　　　　var month = date.getMonth() + 1;
　　　　　var day = date.getDate();
　　　　　if (month < 10) {
    　　　　month = "0" + month;
　　　　　}
　　　　　if (day < 10) {
    　　　　day = "0" + day;
　　　　　}
　　　　　　return year + "-" + month + "-" + day;

　　}
　　return null; 
}