A drop of
JavaScript.

A strict subset of ECMAScript 2027+, implemented from scratch — with a sandbox-first runtime designed for tinkerers, embedding and AI agents.

Open the Playground Read the docs

curl -fsSL https://gocciascript.dev/install | sh

Latest version 0.7.1 released April 29, 2026

View install script Other install options →

Pre-1.0: the API is still in motion — expect breaking changes between any two releases until 1.0.

coffee-typed.ts

// Types, enums, private fields.
type Currency = "USD" | "EUR" | "GBP";

enum DrinkSize {
  Small = "small",
  Medium = "medium",
  Large = "large",
}

interface MenuItem {
  name: string;
  basePrice: number;
}

class CoffeeShop {
  #name: string = "Goccia Coffee";
  #menu: MenuItem[] = [
    { name: "Espresso", basePrice: 2.5 },
    { name: "Latte", basePrice: 4.0 },
  ];

  total(
    items: string[],
    size: DrinkSize,
    currency: Currency,
  ): string {
    const m =
      size === DrinkSize.Large ? 1.3 :
      size === DrinkSize.Medium ? 1.1 : 1.0;
    const sub = items.reduce((s, it) => {
      const f = this.#menu
        .find((x) => x.name === it);
      return s + (f ? f.basePrice * m : 0);
    }, 0);
    const sym: Record<Currency, string> = {
      USD: "$", EUR: "€", GBP: "£",
    };
    return `${sym[currency]}${sub.toFixed(2)}`;
  }

  get name(): string {
    return this.#name;
  }
}

const shop = new CoffeeShop();
const total = shop.total(
  ["Espresso", "Latte"],
  DrinkSize.Medium,
  "EUR",
);
console.log(`Welcome to ${shop.name}!`);
console.log(`Your total: ${total}`);

// Types, enums, private fields.
type Currency = "USD" | "EUR" | "GBP";

enum DrinkSize {
  Small = "small",
  Medium = "medium",
  Large = "large",
}

interface MenuItem {
  name: string;
  basePrice: number;
}

class CoffeeShop {
  #name: string = "Goccia Coffee";
  #menu: MenuItem[] = [
    { name: "Espresso", basePrice: 2.5 },
    { name: "Latte", basePrice: 4.0 },
  ];

total(
    items: string[],
    size: DrinkSize,
    currency: Currency,
  ): string {
    const m =
      size === DrinkSize.Large ? 1.3 :
      size === DrinkSize.Medium ? 1.1 : 1.0;
    const sub = items.reduce((s, it) => {
      const f = this.#menu
        .find((x) => x.name === it);
      return s + (f ? f.basePrice * m : 0);
    }, 0);
    const sym: Record<Currency, string> = {
      USD: "$", EUR: "€", GBP: "£",
    };
    return `${sym[currency]}${sub.toFixed(2)}`;
  }

get name(): string {
    return this.#name;
  }
}

const shop = new CoffeeShop();
const total = shop.total(
  ["Espresso", "Latte"],
  DrinkSize.Medium,
  "EUR",
);
console.log(`Welcome to ${shop.name}!`);
console.log(`Your total: ${total}`);

press Run or ⌘+Enter

Design principles

Modern JavaScript, without the quirks.#

What remains is a small, predictable language with a .

A subset, not a superset

Modern ECMAScript 2027+ — let/const, arrow functions, classes, modules, async/await.

Sandbox-first

No eval, no global mutable state, GET/HEAD-only fetch, timeouts, and explicit global injection via JSON/TOML/YAML.

Explicit over clever

Named imports only. Strict equality only. Descriptive names over shortcuts — even at the cost of verbosity.

A modern standard library, batteries included

Temporal for dates, and direct module imports of JSON, TOML, YAML, CSV, JSONL and Markdown.

Intentionally excluded

What's left out — and why#

Dynamic code construction and scope-changing syntax are left out to keep execution predictable in embedded runtimes. Coercive or legacy forms such as ==, var, and arguments have explicit alternatives. See Language for the per-feature rationale.

Compatibility mode can opt back into selected syntax such as var, function, and ASI via CLI or config flags.

The runtime is also intentionally not Node.js-compatible — no process, no Buffer, no CommonJS, no ambient filesystem globals.

Runtime globals

Beyond the language: the runtime itself#

Everything ECMAScript gives you, plus first-class structured-data formats — direct module imports of .json, .json5, .toml, .yaml, .csv, .tsv, .jsonl, and .md; runtime parsers for each (markdown imports return the raw text); a capability-gated fetch (GET/HEAD only, explicit allow-listed hosts); and a built-in test runner with a Vitest/Jest-compatible test/describe/expect API.

Compiler pipeline

From source to result.#

One pipeline, five stages. Click a stage to jump into the matching docs chapter — start with Architecture.

Step 1 of 5

Source

Every supported extension is the same language — TS/TSX type annotations are parsed and discarded, and JSX is rewritten to function calls in a preprocessing pass before the lexer ever sees it. There is no separate type-checker.

example.js

const price = 2.5;
const qty = 3;
const total = price * qty;
console.log("total:", total);

A drop ofJavaScript.