# Operators Operator expressions are similar to functions that take arguments. | abs | `$abs` | Returns the absolute value of a number | | ---------------- | ------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | acos | `$acos` | Returns a numeric value between 0 and π radians for x between -1 and 1 | | acosh | `$acosh` | Returns the inverse hyperbolic cosine of a number | | acl | `$acl` | Not applicable | | add | `$add` | Adds two or more array properties or expressions. In addition to numbers, a single Date value may be included in the array. | | and | `$and` | Evaluates to **true** if all conditions in the passed in array evaluate to true | | asin | `$asin` | Returns the arcsine (in radians) of a number | | asinh | `$asinh` | Returns the hyperbolic arcsine of a number | | atan | `$atan` | Returns the arctangent (in radians) of a number | | atan2 | `$atan2` | Returns the angle in the plane (in radians) between the positive x-axis and the ray from (0,0) to the point (x,y) | | atanh | `$atanh` | Returns the hyperbolic arctangent of a number | | ceil | `$ceil` | Always rounds a number up to the next largest integer | | convert | `$convert` | Not applicable | | cos | `$cos` | Returns the cosine of the specified angle, which must be specified in radians | | dateFromParts | `$dateFromParts` | Returns a date from the specified parts (year, month, and day values) | | dateFromString | `$dateFromString` | Converts a date object to a string in a specified format, and expects an array of \[date\_expression] | | dateToParts | `$dateToParts` | Returns a document that contains the constituent parts of a given Date value as individual properties | | dateToString | `$dateToString` | Converts a date object to a string according to a user-specified format | | dayOfMonth | `$dayOfMonth` | Returns the day of the month for a date as a number between 1 and 31 | | dayOfWeek | `$dayOfWeek` | Returns the day of the week for a date as a number between 1 (Sunday) and 7 (Saturday) | | dayofYear | `$dayofYear` | Returns the day of the year for a date as a number between 1 and 366 | | degreestoRadians | `$degreestoRadians` | Converts an input value measured in degrees to radians | | divide | `$divide` | Divides one number by another and returns the result | | exp | `$exp` | Takes the e^n of a number | | floor | `$floor` | Returns the largest integer less than or equal to the specified number | | hour | `$hour` | Returns the hour portion of a date as a number between 0 and 23 | | isoDayOfWeek | `$isoDayOfWeek` | Returns the weekday number in ISO 8601 format, ranging from 1 (Monday) to 7 (Sunday) | | isoWeek | `$isoWeek` | Returns the week number in ISO 8601 format, ranging from 1 to 53 | | isoWeekYear | `$isoWeekYear` | Returns the year number in ISO 8601 format | | log | `$log` | Takes the log of the first number in the second number's base | | log10 | `$log10` | Calculates the log base 10 of a number and returns the result as a double | | let | `$let` |

Binds variables for use in the specified expression, and returns the result of the expression

View let for more information on how the let variable is used in mongodb operations.

| | ltrim | `$ltrim` | Removes whitespace characters, including null, or the specified characters from the beginning of a string | | mergeObjects | `$mergeObjects` | Combines multiple documents into a single document | | milliseconds | `$milliseconds` | Returns the millisecond portion of a date as an integer between 0 and 999 | | minute | `$minute` | Returns the minute portion of a date as a number between 0 and 59 | | moment | `$moment` |

Used as a wrapper for the moment.js library to parse, validate, manipulate, and display dates and times in JavaScript

Example to determine the difference between two dates:

$moment: \[date, { 'diff': \[date2, 'days'] }]

| | month | `$month` | Returns the month of a date as a number between 1 and 12 | | multiply | `$multiply` | Multiplies the value of a field by a number | | omit | `$omit` | Not applicable | | or | `$or` | Performs a logical OR operation on an array of two or more and selects the documents that satisfy at least one of the arguments | | pathTo | $pathTo |

Sets a path and creates deep objects

Example:
$pathTo: \[{ $literal: {} }, 'configuration.reporting.enabled', true]

| | pick | `$pick` | Not applicable | | radiansToDegrees | `$radiansToDegrees` | Converts an input value measured in radians to degrees | | regexFind | `$regexFind` | Provides regular expression (regex) pattern matching capability in aggregation expressions | | regexFindAll | `$regexFindAll` | Provides regex pattern matching capability in aggregation expressions. The operator returns an array of documents that contains information on each match. | | regexMatch | `$regexMatch` | Performs regex pattern matching and returns | | replaceAll | `$replaceAll` | Replaces all instances of a search string in an input string with a replacement string | | replaceOne | `$replaceOne` | Replaces the first instance of a search string in an input string with a replacement string | | rtrim | `$rtrim` | Removes whitespace characters, including null, or the specified characters from the end of a string | | second | `$second` | Returns the second portion of a date as a number between 0 and 59, but can be 60 to account for leap seconds | | sin | `$sin` | Returns the sine of a value that is measured in radians | | split | `$split` | Divides a string into an array of substrings based on a delimiter | | sqrt | `$sqrt` | Calculates the square root of a positive number and returns the result as a double | | stdDevPop | `$stdDevPop` | Calculates the population standard deviation of the input values | | stdDevSamp | `$stdDevSamp` | Calculates the sample standard deviation of the input values | | strcasecmp | `$strcasecmp` | Performs a case-insensitive comparison of two strings | | strLenBytes | `$strLenBytes` | Returns the number of UTF-8 encoded bytes in the specified string | | strLenCP | `$strLenCP` | Returns the number of UTF-8 code points in the specified string | | substr | `$substr` | Returns the number of UTF-8 encoded bytes in the specified string | | substrBytes | `$substrBytes` | Returns the substring of a string | | substrCP | `$substrCP` | Returns the substring of a string | | tan | `$tan` | Returns the tangent of a value that is measured in radians | | toDate | `$toDate` | Converts a value to date | | toLower | `$toLower` | Converts a string to lowercase, returning the result | | toUpper | `$toUpper` | Converts a string to uppercase, returning the result | | trim | `$trim` | Removes whitespace characters, including null, or the specified characters from the beginning and end of a string | | week | `$week` | Returns the week of the year for a date as a number between 0 and 53 | | year | `$year` | Returns the year portion of a date |