js 时间格式化

var dtNow = new Date();
      var year = dtNow.getFullYear();
      var month = ('0' + (dtNow.getMonth() + 1)).slice(-2);
      var date = ('0' + dtNow.getDate()).slice(-2);
      var hour = ('0' + dtNow.getHours()).slice(-2);
      var min =('0' + dtNow.getMinutes()).slice(-2);
      var nowStr = year + "-" + month + "-" + date + " " + hour + ":" + min;