$indexOfArray

Definition

Finds an item using Java equality.

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

Syntax

{ "$indexOfArray": [ <array>, <search>, <start>, <end> ] }

Replace angle-bracket placeholders with expressions or values.

Optional parameters may be omitted.

Parameters

Parameter	Required	Description
array	Yes	Expression supplying the source array.
search	Yes	Value or substring to find in the source.
start	No	Starting position or lower bound. See the syntax and examples for this operator.
end	No	Exclusive ending position or upper bound.

Arguments are positional: keep the order shown. The authoring signature accepts 2–4 arguments.

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 array argument:

Input case	Supplied value	Result
null	null	null
missing	Field absent	null
decimal	2.5	Error — $indexOfArray first argument must be an array
numeric string	"12"	Error — $indexOfArray first argument must be an array
text	"hello"	Error — $indexOfArray first argument must be an array
boolean	true	Error — $indexOfArray first argument must be an array
typed date	{"$date":"2026-01-15T15:00:00Z"}	Error — $indexOfArray first argument must be an array
empty array	[]	-1 (int32)
numeric array	[1,2,3]	1 (int32)
object	{"x":1}	Error — $indexOfArray first argument must be an array

Argument handling

Invocation	Result
{"$indexOfArray":[]}	Error — $indexOfArray expects 2 to 4 arguments: [array, search, start?, end?]
{"$indexOfArray":{"unexpected":1}}	Error — $indexOfArray expects 2 to 4 arguments: [array, search, start?, end?]

Examples

Expression:

{
  "$indexOfArray": [
    [
      1,
      2
    ],
    2
  ]
}

Input document:

{}

Observed SrotaX result: 1 (int32).

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: array[0]

Input case	Supplied value	SrotaX result
null	null	null
missing	Field absent	null
zero	0	Error — $indexOfArray first argument must be an array
negative	-2	Error — $indexOfArray first argument must be an array
decimal	2.5	Error — $indexOfArray first argument must be an array
numeric string	"12"	Error — $indexOfArray first argument must be an array
text	"hello"	Error — $indexOfArray first argument must be an array
empty string	""	Error — $indexOfArray first argument must be an array
boolean	true	Error — $indexOfArray first argument must be an array
false	false	Error — $indexOfArray first argument must be an array
typed date	{"$date":"2026-01-15T15:00:00Z"}	Error — $indexOfArray first argument must be an array
decimal128	{"$numberDecimal":"1.25"}	Error — $indexOfArray first argument must be an array
empty array	[]	-1 (int32)
numeric array	[1,2,3]	1 (int32)
mixed array	[1,null,"x",3]	-1 (int32)
nested array	[[1,2],[3]]	-1 (int32)
empty object	{}	Error — $indexOfArray first argument must be an array
object	{"x":1}	Error — $indexOfArray first argument must be an array
ISO date string	"2026-01-15T15:00:00Z"	Error — $indexOfArray first argument must be an array

Argument: search[1]

Input case	Supplied value	SrotaX result
null	null	-1 (int32)
missing	Field absent	-1 (int32)
zero	0	-1 (int32)
negative	-2	-1 (int32)
decimal	2.5	-1 (int32)
numeric string	"12"	-1 (int32)
text	"hello"	-1 (int32)
empty string	""	-1 (int32)
boolean	true	-1 (int32)
false	false	-1 (int32)
typed date	{"$date":"2026-01-15T15:00:00Z"}	-1 (int32)
decimal128	{"$numberDecimal":"1.25"}	-1 (int32)
empty array	[]	-1 (int32)
numeric array	[1,2,3]	-1 (int32)
mixed array	[1,null,"x",3]	-1 (int32)
nested array	[[1,2],[3]]	-1 (int32)
empty object	{}	-1 (int32)
object	{"x":1}	-1 (int32)
ISO date string	"2026-01-15T15:00:00Z"	-1 (int32)

Verification

This page records 41 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: 26 exact BSON matches, 15 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.