icu-to-json

Precompile i18n icu syntax translations to JSON at build time and render them at runtime

Build Time: compile("Hello {name}") → ["Hello ",["name"]]
Run Time: run( ["Hello ",["name"]], { name: "World"} ) → "Hello World"

Goal

The main goal is to boot up javascript apps with ICU translations as fast as possible for the end user.

Therefore this library provides a way to compile ICU MessageFormat strings to compressed JSON at build time and render them at runtime with a minimal runtime footprint.

Features

1. Smaller Runtime Footprint
   The runtime footprint is only 1kb (minified and gzipped)
2. No parsing at runtime
   The precompiled JSON can be rendered without any string parsing at runtime
3. Flexible
   The runtime is able to not only return strings but also any object (aka rich text elements like JSX)
4. Types
   The compiler has an optional feature to generate typescript types for the ICU messages and their arguments

⚠️ the typed t() function is not part of this library. It is only an example how the generated types could be used.

Installation

npm install icu-to-json

Usage

Runtime

Pure Interpolations

import { run } from 'icu-to-json';

// e.g. precompiled icu messsage:
// "Hello {name}!"
run(precompiledMessage, "en", { name: 'World' })) // Hello, World!

Plurals and Selectordinal

import { run } from 'icu-to-json';

// e.g. precompiled icu messsage:
// "You have {count, plural, one {# unread message} other {# unread messages}}."
run(precompiledMessage, "en", { count: 1 })) // You have 1 unread message.

Tags

Tags can be used to wrap parts of the message.

import { run } from 'icu-to-json';

// e.g. precompiled icu messsage:
// "You have <b>{count}</b> messages."
run(precompiledMessage, "en", { count: 2, b: (content: number) => `**${number}**`})) // You have **2** messages.

Rich Text

The runtime is able to not only return strings but also richtext elements (e.g. JSX).
JSX is only used as an example here - it works with any other object as well.

import { evaluateAst } from 'icu-to-json';

// e.g. precompiled icu messsage:
// "You have <link><b>{count, plural, one {# unread message} other {# unread messages}}.</b></link>"
evaluateAst(precompiledMessage, "en", { 
    count: 1, 
    link: (content: string) => <a href="/messages">{content}</a>,
    b: (content: string) => <b>{content}</b>
}) // [ 'You have ', <a href="/messages"><b>1 unread message.</b></a> ]

Compile

CLI

The CLI can be used to compile ICU MessageFormat strings to JSON at build time.

# compile icu messages to json
icu-to-json src/messages.json dist/messages.json
# generate typescript types, locales and formatters from the icu messages
icu-to-json --types src/messages.json dist/messages.json

API

import { compile } from 'icu-to-json/compiler';

const precompiledMessage = compile('Hello {name}!');

Status

This library is still in early development and not yet ready for production use.

How does it work?

The main work is done by the @formatjs/icu-messageformat-parser, which parses the ICU MessageFormat strings and returns an AST. The AST is then traversed and compiled to JSON by icu-to-json.

License

MIT