$dayOfWeek (aggregation operator)（聚合运算符）

Definition定义

$dayOfWeek

Returns the day of the week for a date as a number between 1 (Sunday) and 7 (Saturday).将日期的星期几作为介于1（星期日）和7（星期六）之间的数字返回。

The $dayOfWeek expression has the following operator expression syntax:$dayOfWeek表达式具有以下运算符表达式语法：

{ $dayOfWeek: <dateExpression> }

The argument can be:参数可以是：

• An expression that resolves to a Date, a Timestamp, or an ObjectID.解析为Date、Timestamp或ObjectID的表达式。

• A document with this format:具有此格式的文档：

  { date: <dateExpression>, timezone: <tzExpression> }

  Field字段	Description描述
  date	The date to which the operator is applied. 运算符的应用日期。<dateExpression> must be a valid expression that resolves to a Date, a Timestamp, or an ObjectID.<dateExpression>必须是解析为Date、Timestamp或ObjectID的有效表达式。
  timezone	Optional. 可选。The timezone of the operation result. <tzExpression> must be a valid expression that resolves to a string formatted as either an Olson Timezone Identifier or a UTC Offset. 操作结果的时区。<tzExpression>必须是解析为奥尔森时区标识符或UTC偏移格式的字符串的有效表达式。If no timezone is provided, the result is in UTC.如果没有提供timezone，则结果为UTC。 Format格式 Examples示例 Olson Timezone Identifier奥尔森时区标识符 "America/New_York" "Europe/London" "GMT" UTC OffsetUTC偏移 +/-[hh]:[mm], e.g. "+04:45" +/-[hh][mm], e.g. "-0530" +/-[hh], e.g. "+03"

Behavior行为

{ $dayOfWeek: new Date("2016-01-01") }

{ $dayOfWeek: { date: new Date("Jan 7, 2003") } }

{ $dayOfWeek: {
    date: new Date("August 14, 2011"),
    timezone: "America/Chicago"
} }

{ $dayOfWeek: ISODate("1998-11-07T00:00:00Z") }

{ $dayOfWeek: {
    date: ISODate("1998-11-07T00:00:00Z"),
    timezone: "-0400"
} }

{ $dayOfWeek: "March 28, 1976" }

{ $dayOfWeek: Date("2016-01-01") }

{ $dayOfWeek: "2009-04-09" }

Example示例

Consider a sales collection with the following document:考虑一个带有以下文档的sales集合：

 db.sales.insertOne(
  {
   "_id" : 1,
   "item" : "abc",
   "price" : 10,
   "quantity" : 2,
   "date" : ISODate("2014-01-01T08:15:39.736Z")
  }
)

The following aggregation uses the $dayOfWeek and other date operators to break down the date field:以下聚合使用$dayOfWeek和其他日期运算符来分解date字段：

db.sales.aggregate(
   [
     {
       $project:
         {
           year: { $year: "$date" },
           month: { $month: "$date" },
           day: { $dayOfMonth: "$date" },
           hour: { $hour: "$date" },
           minutes: { $minute: "$date" },
           seconds: { $second: "$date" },
           milliseconds: { $millisecond: "$date" },
           dayOfYear: { $dayOfYear: "$date" },
           dayOfWeek: { $dayOfWeek: "$date" },
           week: { $week: "$date" }
         }
     }
   ]
)

The operation returns the following result:该操作返回以下结果：

{
  "_id" : 1,
  "year" : 2014,
  "month" : 1,
  "day" : 1,
  "hour" : 8,
  "minutes" : 15,
  "seconds" : 39,
  "milliseconds" : 736,
  "dayOfYear" : 1,
  "dayOfWeek" : 4,
  "week" : 0
}