fromjson

Fromjson is a term used in software libraries to describe a function or operator that converts a JSON-formatted text string into native data structures. The exact name, syntax, and behavior vary by language and framework; some libraries capitalize the JSON segment (fromJSON), others use lowercase with underscores (from_json) or provide a generic parse function (json.loads, JSON.parse). In many data-processing environments, fromjson is specifically used to convert a JSON string into a structured representation that mirrors JSON objects and arrays, sometimes with optional schema enforcement.

In R, the fromJSON function provided by the jsonlite package maps JSON data to R lists, vectors, data frames, or factors, with optional simplification and flattening. In Apache Spark, from_json is a SQL function that parses a JSON string column into a struct or other composite type, guided by an explicit schema; it is commonly used in data pipelines that ingest JSON payloads. Other ecosystems offer similar functionality under different names, such as Python's json.loads, JavaScript's JSON.parse, or Java's Gson and Jackson libraries.

Usage considerations include error handling for malformed input, performance implications on large strings, and security concerns when parsing untrusted data. Some implementations support streaming or incremental parsing; others require the complete JSON string upfront. In strongly typed contexts, fromjson often enforces a predefined schema to ensure the resulting object matches expected fields and types.

See also: JSON, JSON parsing, data deserialization, schema.