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$ltrim

Definition

Trims configured characters from the start of text.

Expression operator · Text · Studio Visual: available. Studio validates the complete expression separately.

Syntax

{
  "$ltrim": {
    "input": <input>,
    "chars": <chars>
  }
}

Replace angle-bracket placeholders with expressions or values.

Optional parameters may be omitted.

Parameters

Parameter Required Description
input Yes Expression supplying the value to process. A field reference such as "$price" reads from the current document.
chars No Characters to remove from the ends of the string. If omitted, the operator uses its whitespace trimming behavior.

Behavior

The following observations use the example expression below. Each row substitutes one argument while retaining the other example arguments. A missing field differs from an explicit null; the result shown is what Core actually returned.

For the input argument:

Input case Supplied value Result
null null null
missing Field absent null
decimal 2.5 Error — $trim input must be a string
numeric string "12" "12"
text "hello" "hello"
boolean true Error — $trim input must be a string
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $trim input must be a string
empty array [] Error — $trim input must be a string
numeric array [1,2,3] Error — $trim input must be a string
object {"x":1} Error — $trim input must be a string

Argument handling

Invocation Result
{"$ltrim":[]} Error — $trim requires input and optional chars
{"$ltrim":{"unexpected":1}} Error — $trim requires input and optional chars

Examples

Expression: 

{
  "$ltrim": {
    "input": "  hi"
  }
}

Input document: 

{}

Observed SrotaX result: "hi".

Detailed input cases

Expand the complete argument-by-argument test matrix

Each table changes only the indicated argument from the example above. Other arguments retain their baseline values. Values normally come from the input field probe; literal configuration arguments are replaced directly. “Missing” means the field is absent, not explicitly null. Numeric strings are strings, not numbers.

Argument: input

Input case Supplied value SrotaX result
null null null
missing Field absent null
zero 0 Error — $trim input must be a string
negative -2 Error — $trim input must be a string
decimal 2.5 Error — $trim input must be a string
numeric string "12" "12"
text "hello" "hello"
empty string "" ""
boolean true Error — $trim input must be a string
false false Error — $trim input must be a string
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $trim input must be a string
decimal128 {"$numberDecimal":"1.25"} Error — $trim input must be a string
empty array [] Error — $trim input must be a string
numeric array [1,2,3] Error — $trim input must be a string
mixed array [1,null,"x",3] Error — $trim input must be a string
nested array [[1,2],[3]] Error — $trim input must be a string
empty object {} Error — $trim input must be a string
object {"x":1} Error — $trim input must be a string
ISO date string "2026-01-15T15:00:00Z" "2026-01-15T15:00:00Z"
omitted named argument Argument removed Error — $trim requires input and optional chars

Argument: chars

Input case Supplied value SrotaX result
null null null
missing Field absent null
zero 0 Error — $trim chars must be a string
negative -2 Error — $trim chars must be a string
decimal 2.5 Error — $trim chars must be a string
numeric string "12" " hi"
text "hello" " hi"
empty string "" " hi"
boolean true Error — $trim chars must be a string
false false Error — $trim chars must be a string
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $trim chars must be a string
decimal128 {"$numberDecimal":"1.25"} Error — $trim chars must be a string
empty array [] Error — $trim chars must be a string
numeric array [1,2,3] Error — $trim chars must be a string
mixed array [1,null,"x",3] Error — $trim chars must be a string
nested array [[1,2],[3]] Error — $trim chars must be a string
empty object {} Error — $trim chars must be a string
object {"x":1} Error — $trim chars must be a string
ISO date string "2026-01-15T15:00:00Z" " hi"
omitted named argument Argument removed "hi"

Verification

This page records 43 executed cases. It covers individual argument substitutions, not every cross-product of arguments, locale, daylight-saving transitions, numeric overflow, collation or resource limits. No untested behavior is guaranteed.

Download exact expressions, inputs and SrotaX results. Errors are observed messages, not stable public error codes. The reference generator reads the checked-in execution report; do not edit generated observations by hand.

MongoDB differences

Compared with MongoDB 9.0.4: 14 exact BSON matches, 29 both rejected, 0 value/type/acceptance differences, 0 object-field-order differences.

“Exact” includes numeric BSON types and object key order. A value of 3 as int32 differs from 3.0 as double. Object-field-order differences are reported separately; object key ordering is not enforced by the engine regression baseline. Both rejected does not mean the error codes or messages match. This is finite-case evidence, not full compatibility certification.

No differences were observed in the compared cases.

Download full comparison evidence.