FunctionalScript
FunctionalScript is a safe, purely functional programming language and a strict subset of
ECMAScript/JavaScript. It's inspired by
- JSON and JSON5 as subsets of JavaScript values.
JSON is also a subset of FunctionalScript values.
- asm.JS (a precursor of WebAssembly),
as a subset of JavaScript.
- TypeScript, as a superset of JavaScript.
Its abbreviation is FJS.
The FunctionalScript specification describes the language
the compiler accepts today; features not implemented yet are in
spec/todo/.
Learn more about
This repository is a monorepo and distributed under MIT.
Getting Started
Install FunctionalScript via npm:
npm install -g functionalscript
or run the CLI without installing it, with npx functionalscript <command>.
Compiling a module
A FunctionalScript module is already a JavaScript module, so nothing has to be
compiled to run it. fjs compile goes the other way: it resolves every
import and writes the language the output name declares. The value outputs,
.json and .data.js, initialize the complete module and its required
dependencies, then serialize only the default export as data. Calls and
operators can compute that data; a function remaining in the selected result
is refused.
The graph outputs, .js, .edag.data.js and .rs, preserve the program
without running module initialization, including functions, calls and
operators within each output's supported profile. The .js writer supports
ordinary and method calls, spreads and operators, but remains partial: it
refuses graph shapes it cannot reconstruct as FunctionalScript source. See
the output contracts and limits.
// m.f.js
export default ["text"];
// input.f.js
import c from "./m.f.js";
const a = 1;
export default [a, a, c, { x: c }];
fjs compile input.f.js output.data.js # DataJS
fjs compile input.f.js output.js # FunctionalScript
fjs compile input.f.js output.json # JSON
fjs compile input.f.js output.edag.data.js # the program's EDAG
fjs compile input.f.js output.rs # a generated nanvm-lib module
Each .js name has an .mjs twin — .data.mjs, .mjs, .edag.data.mjs —
for a file that must load as an ES module whatever the package's "type" says.
c is one array reached twice, so output.data.js keeps it shared:
const $0=["text"];export default [1,1,$0,{"x":$0}];
JSON is a tree and carries no identity, so output.json writes the array
where each reference reaches it, as JSON.stringify does:
[1,1,["text"],{"x":["text"]}]
The specification is the reference for what the compiler
accepts, and its Output section says what each
output writes or refuses.
The fjs CLI
Run fjs help to print the available commands, or see
fjs/README.md for the full CLI reference. Commands also accept
short aliases, which fjs help prints; the documentation spells them out
instead.
Vision
We aim to create a safe, cross-platform programming language that can work in any JS platform without any build step. There are thousands of programming languages, and we don't want to create another one that others must learn. Instead, we take the opposite approach: we remove everything that makes the most popular and cross-platform language unsafe, insecure, or less portable.
Applications
FunctionalScript code can be used:
- safely in any JavaScript/TypeScript application or library;
- as a JSON with expressions, see DJS;
- as a query language;
- as a smart contract programming language in DeFi.
Design Principles
In FunctionalScript:
- Any module is a valid JavaScript module. No additional build steps are required.
- Code should not have side-effects. Any JavaScript statement, expression, or function that has a side effect is not allowed in FunctionalScript. There are no exceptions to this rule, such as
unsafe code, which can be found in Rust, C#, and other languages.
- A module can depend only on another FunctionalScript module.
- It also has no standard library. Only a safe subset of standard JavaScript API can be used without referencing other modules.
Sponsors
