$convert (expression operator)（表达式运算符）

{ input: true, to: "bool" }

{ input: false, to: "bool" }

{ input: 1.99999, to: "bool" }

{ input: Decimal128( "5" ), to: "bool" }

{ input: Decimal128( "0" ), to: "bool" }

{ input: 100, to: "bool" }

{
   input: ISODate( "2018-03-26T04:38:28.044Z" ),
   to: "bool"
}

{ input: "hello", to: "bool" }

{ input: "false", to: "bool" }

{ input: "", to: "bool" }

{ input: null, to: "bool" }

Returns the binData value as an integer. binData is interpreted as two's signed complement signed integer.以整数形式返回binData值。binData被解释为2的带符号补码带符号整数。

The number of bytes in the binData value must be 1, 2, or 4.binData值中的字节数必须为1、2或4。

If the input is of an unexpected length an error is generated. You can control this behavior by configuring $convert.onError.如果input的长度超出预期，则会生成错误。您可以通过配置$convertonError来控制此行为。

Returns truncated value.返回截断值。

The truncated double value must fall within the minimum and maximum value for an integer.截断的双精度值必须落在整数的最小值和最大值之间。

You cannot convert a double value whose truncated value is less than the minimum integer value or is greater than the maximum integer value.您无法转换截断值小于最小整数值或大于最大整数值的双精度值。

Returns truncated value.返回截断值。

The truncated decimal value must fall within the minimum and maximum value for an integer.截断的十进制值必须落在整数的最小值和最大值之间。

You cannot convert a decimal value whose truncated value is less than the minimum integer value or is greater than the maximum integer value.截断值小于最小整数值或大于最大整数值的十进制值无法转换。

Returns the long value as an integer.以整数形式返回长值。

The long value must fall within the minimum and maximum value for an integer.长值必须落在整数的最小值和最大值之间。

You cannot convert a long value that is less than the minimum integer value or is greater than the maximum integer value.您无法转换小于最小整数值或大于最大整数值的长值。

Returns the numerical value of the string as an integer.以整数形式返回字符串的数值。

The string value must be a base ₁₀ integer (e.g. "-5", "123456") and fall within the minimum and maximum value for an integer.字符串值必须是以10为底的整数（例如"-5"、"123456"），并且在整数的最小值和最大值范围内。

You cannot convert a string value of a float or decimal or non-base ₁₀ number (e.g. "-5.0", "0x6400") or a value that falls outside the minimum and maximum value for an integer.您不能转换浮点数、十进制数或非十进制数（例如"-5.0"、"0x6400"）的字符串值，也不能转换整数的最小值和最大值之外的值。

{ input: true, to: "int" }

{ input: false, to: "int" }

{ input: 1.99999, to: "int" }

{ input: Decimal128( "5.5000" ), to: "int" }

{
   input: Decimal128( "9223372036000.000" ),
   to: "int"
}

{ input: Long( "5000" ), to: "int" }

{ input: Long( "922337203600" ), to: "int" }

{ input: "-2", to: "int" }

{ input: "2.5", to: "int" }

{ input: null, to: "int" }

{
   input: Binary(Buffer.from("00100000", "hex"), 0),
   to: "int",
   byteOrder: "big",
}

{
   input: Binary(Buffer.from("FFFFE796", "hex"), 0),
   to: "int",
}

{
   input: Binary(Buffer.from("001000000000000", "hex"), 0),
   to: "int",
   byteOrder: "big",
}

Returns the numerical value of the string as a decimal.以十进制形式返回字符串的数值。

The string value must be of a base ₁₀ numeric value (e.g. "-5.5", "123456").字符串值必须是以10为底的数值（例如"-5.5"、"123456"）的字符串值。

You cannot convert a string value of a non-base ₁₀ number (e.g. "0x6400")您无法转换非十进制数字的字符串值（例如"0x6400"）

{ input: true, to: "decimal" }

{ input: false, to: "decimal" }

{ input: 2.5, to: "decimal" }

{ input: Int32( 5 ), to: "decimal" }

{ input: Long( 10000 ), to: "decimal" }

{ input: "-5.5", to: "decimal" }

{
   input: ISODate( "2018-03-26T04:38:28.044Z" ),
   to: "decimal"
}

Returns the binData value as a double. binData is interpreted as an IEEE 754 single-precision or double-precision floating point.以double形式返回binData值。binData被解释为IEEE 754单精度或双精度浮点。

The number of bytes in the binData value must be 4 or 8.binData值中的字节数必须为4或8。

If the input is of an unexpected length an error is generated. You can control this behavior by configuring $convert.onError.如果input的长度超出预期，则会生成错误。您可以通过配置$convert.onError来控制此行为。

Returns the decimal value as a double.以双精度函数的形式返回十进制值。

The decimal value must fall within the minimum and maximum value for a double.小数值必须落在双精度的最小值和最大值之间。

You cannot convert a decimal value whose value is less than the minimum double value or is greater than the maximum double value.不能转换值小于最小双精度值或大于最大双精度值的十进制值。

Returns the numerical value of the string as a double.以double形式返回字符串的数值。

The string value must be of a base ₁₀ numeric value (e.g. "-5.5", "123456") and fall within the minimum and maximum value for a double.字符串值必须是以10为底的数值（例如"-5.5"、"123456"）的字符串值，并且在双精度的最小值和最大值范围内。

You cannot convert a string value of a non-base ₁₀ number (e.g. "0x6400") or a value that falls outside the minimum and maximum value for a double.您无法转换非十进制数字的字符串值（例如"0x6400"）或超出双精度最小值和最大值的值。

{ input: true, to: "double" }

{ input: false, to: "double" }

{ input: 2.5, to: "double" }

{ input: Int32( 5 ), to: "double" }

{ input: Long( "10000" ), to: "double" }

{ input: "-5.5", to: "double" }

{ input: "5e10", to: "double" }

{
   input: ISODate( "2018-03-26T04:38:28.044Z" ),
   to: "double"
}

{
   input: Binary(Buffer.from("04CCCCCD", "hex"), 0),
   to: "double",
   byteOrder: "big",
}

{
   input: Binary(Buffer.from("0000", "hex"), 0),
   to: "double",
   byteOrder: "big",
}

Returns the binData value as a long. binData is interpreted as two's signed complement signed integer.以long形式返回binData值。binData被解释为2的带符号补码带符号整数。

The number of bytes in the binData value must be 1, 2, 4 or 8.binData值中的字节数必须为1、2、4或8。

If the input is of an unexpected length an error is generated. You can control this behavior by configuring $convert.onError.如果input的长度超出预期，则会生成错误。您可以通过配置$convert.onError来控制此行为。

Returns truncated value.返回截断值。

The truncated double value must fall within the minimum and maximum value for a long.截断的双精度值必须在长时间内落在最小值和最大值之间。

You cannot convert a double value whose truncated value is less than the minimum long value or is greater than the maximum long value.您无法转换截断值小于最小长值或大于最大长值的双精度值。

Returns truncated value.返回截断值。

The truncated decimal value must fall within the minimum and maximum value for a long.截断的十进制值必须长时间处于最小值和最大值之间。

You cannot convert a decimal value whose truncated value is less than the minimum long value or is greater than the maximum long value.截断值小于最小长值或大于最大长值的十进制值无法转换。

Returns the numerical value of the string.返回字符串的数值。

The string value must be of a base ₁₀ long (e.g. "-5", "123456") and fall within the minimum and maximum value for a long.字符串值必须是以10为底的长整型（例如"-5"、"123456"）的字符串值，并且在一个long的最小值和最大值范围内。

You cannot convert a string value of a float or decimal or non-base ₁₀ number (e.g. "-5.0", "0x6400") or a value that falls outside the minimum and maximum value for a long.您不能转换浮点数、十进制数或非十进制数（例如"-5.0"、"0x6400"）的字符串值，也不能转换长时间不在最小值和最大值范围内的值。

{ input: true, to: "long" }

{ input: false, to: "long"  }

{ input: 2.5, to: "long"  }

{ input: Decimal128( "5.5000" ), to: "long" }

{
   input: Decimal128( "9223372036854775808.0" ),
   to: "long"
}

{ input: Int32( 8 ), to: "long" }

{
   input: ISODate( "2018-03-26T04:38:28.044Z" ),
   to: "long"
}

{ input: "-2", to: "long" }

{ input: "2.5", to: "long" }

{ input: null, to: "long" }

{
   input: Binary(Buffer.from("001000000", "hex"), 0),
   to: "long",
   byteOrder: "big",
}

Returns a date that corresponds to the number of milliseconds represented by the truncated double value.返回一个日期，该日期对应于截断的双精度值所表示的毫秒数。

Positive number corresponds to the number of milliseconds since Jan 1, 1970.正数对应自1970年1月1日以来的毫秒数。

Negative number corresponds to the number of milliseconds before Jan 1, 1970.负数对应于1970年1月1日之前的毫秒数。

Returns a date that corresponds to the number of milliseconds represented by the truncated decimal value.返回与截断的十进制值表示的毫秒数对应的日期。

Positive number corresponds to the number of milliseconds since Jan 1, 1970.正数对应自1970年1月1日以来的毫秒数。

Negative number corresponds to the number of milliseconds before Jan 1, 1970.负数对应于1970年1月1日之前的毫秒数。

Returns a date that corresponds to the number of milliseconds represented by the long value.返回与long值表示的毫秒数对应的日期。

Positive number corresponds to the number of milliseconds since Jan 1, 1970.正数对应自1970年1月1日以来的毫秒数。

Negative number corresponds to the number of milliseconds before Jan 1, 1970.负数对应于1970年1月1日之前的毫秒数。

Returns a date that corresponds to the date string.返回与日期字符串对应的日期。

The string must be a valid date string, such as:字符串必须是有效的日期字符串，例如：

• "2018-03-03"
• "2018-03-03T12:00:00Z"
• "2018-03-03T12:00:00+0500"

{
   input: 120000000000.5,
   to: "date"
}

{
   input: Decimal128( "1253372036000.50" ),
   to: "date"
}

{
   input: Long( "1100000000000" ),
   to: "date
}

{
   input:  Long( "-1100000000000" ),
   to: "date"
}

{
   input: ObjectId( "5ab9c3da31c2ab715d421285" ),
   to: "date"
}

{ input:  "2018-03-03", to: "date" }

{
   input: "2018-03-20 11:00:06 +0500",
   to: "date"
}

{ input: "Friday", to: "date" }

{
   input: Timestamp( { t: 1637688118, i: 1 } ),
   to: "date"
}

Returns an ObjectId for the hexadecimal string of length 24.返回长度为24的十六进制字符串的ObjectId。

You cannot convert a string value that is not a hexadecimal string of length 24.您无法转换长度不是24的十六进制字符串的字符串值。

{
   input: "5ab9cbfa31c2ab715d42129e",
   to: "objectId"
}

{
   input: "5ab9cbfa31c2ab715d42129",
   to: "objectId"
}

{ input: true, to: "string" }

{ input: false, to: "string" }

{ input: 2.5, to: "string" }

{ input: Int32( 2 ), to: "string" }

{ input:  Long( 1000 ), to: "string" }

{
   input: ObjectId( "5ab9c3da31c2ab715d421285" ),
   to: "string"
}

{
   input:  ISODate( "2018-03-27T16:58:51.538Z" ),
   to: "string"
}

{
   input: BinData(4, "hn3f"),
   to: "string",
   format: "base64"
}