Bun.JSONL object | API Reference | Bun

JSONL (JSON Lines) related APIs.

Each line in the input is expected to be a valid JSON value separated by newlines.

The result of Bun.JSONL.parseChunk.

true if all input was consumed successfully. false if the input ends with an incomplete value or a parse error occurred.

A SyntaxError if a parse error occurred, otherwise null. Values parsed before the error are still available in values.

How far into the input was consumed. When the input is a string, this is a character offset. When the input is a TypedArray, this is a byte offset. Use input.slice(read) or input.subarray(read) to get the unconsumed remainder.

The successfully parsed JSON values.

Parse a JSONL (JSON Lines) string into an array of JavaScript values.

If a parse error occurs and no values were successfully parsed, throws a SyntaxError. If values were parsed before the error, returns the successfully parsed values without throwing.

Incomplete trailing values (e.g. from a partial chunk) are silently ignored and not included in the result.

When a TypedArray is passed, the bytes are parsed directly without copying if the content is ASCII.

The JSONL string or typed array to parse

An array of parsed values

const items = Bun.JSONL.parse('{"a":1}\n{"b":2}\n');
// [{ a: 1 }, { b: 2 }]

// From a Uint8Array (zero-copy for ASCII):
const buf = new TextEncoder().encode('{"a":1}\n{"b":2}\n');
const items = Bun.JSONL.parse(buf);
// [{ a: 1 }, { b: 2 }]

// Partial results on error after valid values:
const partial = Bun.JSONL.parse('{"a":1}\n{bad}\n');
// [{ a: 1 }]

// Throws when no valid values precede the error:
Bun.JSONL.parse('{bad}\n'); // throws SyntaxError

Parse a JSONL chunk, designed for streaming use.

Never throws on parse errors. Instead, returns whatever values were successfully parsed along with an error property containing the SyntaxError (or null on success). Use read to determine how much input was consumed and done to check if all input was parsed.

When a TypedArray is passed, the bytes are parsed directly without copying if the content is ASCII. Optional start and end parameters select a window of the input without copying. For typed arrays these are byte offsets and read will be a byte offset into the original typed array. For strings these are character offsets and read will be a character offset into the original string.

The JSONL string or typed array to parse

Offset to start parsing from (bytes for typed arrays, characters for strings, default: 0)

Offset to stop parsing at (bytes for typed arrays, characters for strings, default: input length)

An object with values, read, done, and error properties

let buffer = new Uint8Array(0);
for await (const chunk of stream) {
buffer = Buffer.concat([buffer, chunk]);
const { values, read, error } = Bun.JSONL.parseChunk(buffer);
if (error) throw error;
for (const value of values) handle(value);
buffer = buffer.subarray(read);
}