# JSON Array

Key: `container.object.json_array`

JSON array format: \[val1, val2, val3, ...\]. May contain objects, scalars, or nested arrays.

Page: <https://meridian.online/docs/projects/finetype/types/container/object/json_array>

Samples: `[1, 2, 3]`, `["a", "b", "c"]`, `[{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}]`

## Background

### Origin

RFC 8259 defines an array in JSON as an ordered sequence of zero or more values.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) RFC 8259 says the terms "object" and "array" come from the conventions of JavaScript.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) RFC 8259 describes JSON as derived from the object literals of JavaScript, as defined in the ECMAScript Programming Language Standard, Third Edition.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) RFC 8259 gives JSON's design goals as being minimal, portable, textual and a subset of JavaScript.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt)

RFC 8259 says RFC 4627 originally described JSON and registered the media type application/json.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) Ecma International publishes JSON as ECMA-404, The JSON data interchange syntax, whose 2nd edition is dated December 2017.[[2]](https://ecma-international.org/publications-and-standards/standards/ecma-404/) ECMA-404's 1st edition was published in October 2013.[[2]](https://ecma-international.org/publications-and-standards/standards/ecma-404/) ECMA-404 is also numbered ISO/IEC 21778.[[2]](https://ecma-international.org/publications-and-standards/standards/ecma-404/)

RFC 8259 writes an array as square brackets surrounding zero or more values, with the elements separated by commas.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) RFC 8259 places no requirement that the values in an array be of the same type.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt)

### Use

PostgreSQL's json data type stores an exact copy of the input text, preserving semantically-insignificant white space between tokens.[[3]](https://www.postgresql.org/docs/current/datatype-json.html) PostgreSQL's documentation says most applications should generally prefer to store JSON data as jsonb.[[3]](https://www.postgresql.org/docs/current/datatype-json.html) In PostgreSQL's jsonb containment test, the order of array elements is not significant, so '\[1, 2, 3\]'::jsonb @\> '\[3, 1\]'::jsonb is true.[[3]](https://www.postgresql.org/docs/current/datatype-json.html)

DuckDB's json\_structure function defaults to JSON when the structure is inconsistent, such as incompatible types in an array.[[4]](https://duckdb.org/docs/current/data/json/json_functions) DuckDB's documentation gives json\_structure('\["duck", {"family": "anatidae"}\]') as returning \["JSON"\].[[4]](https://duckdb.org/docs/current/data/json/json_functions) DuckDB's json\_array\_length function returns the number of elements in a JSON array, or 0 if the value is not a JSON array.[[4]](https://duckdb.org/docs/current/data/json/json_functions) DuckDB uses 1-based indexing for its ARRAY and LIST data types but 0-based indexing for the JSON data type, following PostgreSQL's conventions.[[5]](https://duckdb.org/docs/current/data/json/overview) When an array column lands in a typed list, check whether every index you carried over from the JSON side needs shifting by one. (Meridian's view)

RFC 8259 allows a JSON parser to set limits on the maximum depth of nesting and on the size of texts it accepts.[[1]](https://www.rfc-editor.org/rfc/rfc8259.txt) Long numeric identifiers inside an array are safer kept as strings, or parsed with a decimal or 64-bit integer type, than read as floating point. (Meridian's view) A bracketed value in a CSV column is not always JSON: single-quoted lists and other near-JSON forms can look much the same, so validate with a real JSON parser rather than a pattern that only checks the brackets. (Meridian's view)

## Sources

1. [The JavaScript Object Notation (JSON) Data Interchange Format](https://www.rfc-editor.org/rfc/rfc8259.txt) — standard
2. [ECMA-404 - Ecma International](https://ecma-international.org/publications-and-standards/standards/ecma-404/) — catalogue entry
3. [PostgreSQL: Documentation: 18: 8.14. JSON Types](https://www.postgresql.org/docs/current/datatype-json.html) — documentation
4. [JSON Processing Functions – DuckDB](https://duckdb.org/docs/current/data/json/json_functions) — documentation
5. [JSON Overview – DuckDB](https://duckdb.org/docs/current/data/json/overview) — documentation