js-toml

A TOML parser for JavaScript and TypeScript. Fully tested and 100% compatible with the TOML v1.1.0 spec (every valid TOML v1.0.0 document parses identically; dump() keeps emitting TOML v1.0.0-compatible output for maximum downstream compatibility). Passes all 681 cases of the official toml-test suite. Support Node.js, browsers and Bun⚡️!

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Trusted By

js-toml is used by leading companies and major open-source projects, including:

• MongoDB (in the snooty documentation compiler)
• LINE (in abc-user-feedback)
• cargo-lambda (in cargo-lambda-cdk, the CDK construct for deploying Rust on AWS Lambda)
• Mise (a next-gen asdf)
• Open edX (in over 28 packages)
• ... and many more.

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Installation

npm install js-toml

or with yarn

yarn add js-toml

or with pnpm

pnpm add js-toml

even support bun!

bun add js-toml

Usage

Parsing TOML

import {load} from 'js-toml';

const toml = `
title = "TOML Example"

[owner]
name = "Tom Preston-Werner"
dob = 1979-05-27T07:32:00-08:00 # First class dates
`;

const data = load(toml);
console.log(data);

Serializing to TOML

import {dump} from 'js-toml';

const toml = dump({
  title: 'TOML Example',
  owner: {
    name: 'Tom Preston-Werner',
    dob: new Date('1979-05-27T07:32:00-08:00'),
  },
});

console.log(toml);

API

load(toml: string, options?: LoadOptions): object

Parses a TOML string and returns a JavaScript object.

LoadOptions

Option	Type	Default	Description
maxDepth	number	100	Maximum nesting depth for arrays / inline tables and dotted-key / table-header segments. Input exceeding this is rejected with a SyntaxParseError instead of overflowing the call stack with a RangeError.

Any invalid input, including input that exceeds maxDepth, is reported by throwing SyntaxParseError.

Dates and times

TOML type	Example	You get
Offset date-time	1979-05-27T07:32:00Z	TomlDate at that instant
Local date-time	1979-05-27T07:32:00	TomlDate, wall clock read as UTC
Local date	1979-05-27	TomlDate at midnight UTC
Local time	07:32:00	TomlTime, a Date with no day

A local date-time carries no offset, so read it with getUTCHours() and friends; getHours() would shift with the host timezone.

All four are Date subclasses, so instanceof Date reaches every one and toISOString() returns the form the document wrote rather than an instant with a Z it never carried. JSON.stringify follows, since toJSON delegates there. TomlDate adds kind, one of 'offset-date-time', 'local-date-time' or 'local-date'; TomlTime adds hour, minute, second and fraction, and keeps the source precision that a millisecond-based encoding rounds away.

Upgrading from 1.x? MIGRATION.md is a search table for the date/time changes, all of which are silent.

dump(object: object, options?: DumpOptions): string

Serializes a JavaScript object into a TOML string. The input must be a plain object (i.e. a TOML table).

Supported value types: string, number, bigint, boolean, Date, array, plain object, and array-of-tables. Strings are always emitted as single-line basic strings; multiline string output is not currently supported.

DumpOptions

Option	Type	Default	Description
newline	'\n' | '\r\n'	'\n'	Newline sequence used between lines.
ignoreUndefined	boolean	false	If true, properties with unsupported values (undefined, Symbol, Function) are silently dropped instead of throwing.
forceQuotes	boolean	false	If true, string keys are always quoted, even when they only contain bare-key characters.

License

MIT

References

TOML v1.1.0 Official Specs

TOML GitHub Project

TOML Test

iarna-toml