$toObject
Definition
Parses a strict JSON string into an object.
Expression operator · Types and conversion · Studio Visual: available. Studio validates the complete expression separately.
Syntax
{ "$toObject": <expression> }
Replace angle-bracket placeholders with expressions or values.
String containing a JSON object. Existing object values are rejected; this operator parses strings.
The value goes directly after the operator name; do not add an input wrapper.
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 — Container conversion requires a JSON string |
| numeric string | "12" | Error — JSON root must be object |
| text | "hello" | Error — Invalid JSON container |
| boolean | true | Error — Container conversion requires a JSON string |
| typed date | {"$date":"2026-01-15T15:00:00Z"} | Error — Container conversion requires a JSON string |
| empty array | [] | Error — Container conversion requires a JSON string |
| numeric array | [1,2,3] | Error — Container conversion requires a JSON string |
| object | {"x":1} | Error — Container conversion requires a JSON string |
Argument handling
| Invocation | Result |
|---|---|
| {"$toObject":[]} | Error — Container conversion requires a JSON string |
| {"$toObject":{"unexpected":1}} | Error — Container conversion requires a JSON string |
Examples
Expression:
{
"$toObject": "{\"name\":\"Alex\"}"
}
Input document:
{}
Observed SrotaX result: {"name":"Alex"}.
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 — Container conversion requires a JSON string |
| negative | -2 | Error — Container conversion requires a JSON string |
| decimal | 2.5 | Error — Container conversion requires a JSON string |
| numeric string | "12" | Error — JSON root must be object |
| text | "hello" | Error — Invalid JSON container |
| empty string | "" | Error — Invalid JSON container |
| boolean | true | Error — Container conversion requires a JSON string |
| false | false | Error — Container conversion requires a JSON string |
| typed date | {"$date":"2026-01-15T15:00:00Z"} | Error — Container conversion requires a JSON string |
| decimal128 | {"$numberDecimal":"1.25"} | Error — Container conversion requires a JSON string |
| empty array | [] | Error — Container conversion requires a JSON string |
| numeric array | [1,2,3] | Error — Container conversion requires a JSON string |
| mixed array | [1,null,"x",3] | Error — Container conversion requires a JSON string |
| nested array | [[1,2],[3]] | Error — Container conversion requires a JSON string |
| empty object | {} | Error — Container conversion requires a JSON string |
| object | {"x":1} | Error — Container conversion requires a JSON string |
| ISO date string | "2026-01-15T15:00:00Z" | Error — Invalid JSON container |
Additional boundary examples
Show 19 tested examples
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "{\"a\":1,\"a\":2,\"nested\":{\"$date\":\"2020\"},\"x\":[1,2]}"
}
SrotaX: {"a":2,"nested":{"$date":"2020"},"x":[1,2]}.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": null
}
SrotaX: null.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": ""
}
SrotaX: Error — Invalid JSON container.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "null"
}
SrotaX: Error — JSON root must be object.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "123"
}
SrotaX: Error — JSON root must be object.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "true"
}
SrotaX: Error — JSON root must be object.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "[]"
}
SrotaX: Error — JSON root must be object.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "{}"
}
SrotaX: {}.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "[1,]"
}
SrotaX: Error — Invalid JSON container.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "{\"x\":1,}"
}
SrotaX: Error — Invalid JSON container.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "/*x*/ []"
}
SrotaX: Error — Invalid JSON container.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "[] {}"
}
SrotaX: Error — Invalid JSON container.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "{\"x\\u0000\":1}"
}
SrotaX: Error — JSON field names cannot contain null bytes.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "{\"x\":\"a\\u0000b\"}"
}
SrotaX: {"x":"a\u0000b"}.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": "[1e400]"
}
SrotaX: Error — JSON root must be object.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": 123
}
SrotaX: Error — Container conversion requires a JSON string.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": []
}
SrotaX: Error — Container conversion requires a JSON string.
Expression:
{
"$toObject": "$value"
}
Input:
{
"value": {}
}
SrotaX: Error — Container conversion requires a JSON string.
Expression:
{
"$toObject": "$missing"
}
Input:
{}
SrotaX: null.
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: 8 exact BSON matches, 33 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.