# zJs (asset type) A zJs asset is a JavaScript ES module: a `<name>.zJs/` folder whose `main.js` holds JavaScript source parsed and evaluated by the `zerojs` interpreter. The identity is `<name>` (the `.zJs` suffix strips). ## Folder shape - `main.js` — the module body. **Required.** - `README.md` — instance documentation. **Required.** - `.metadata` — tags sidecar (`{"tags": []}`). **Required.** ## How to create one ```luau asset.create("zJs", "greeter") -- Creates /zero/source/greeter.zJs/ with a hello-world main.js. asset.create("zJs", "greeter", { source = "export const x = 1" }) -- main.js is the given source verbatim. ``` ## Static diagnostics Every write to `main.js` reparses the module and resolves its import specifiers against the live asset index. `asset.resolve("<name>", "zJs"):check()` returns `{ ok, diagnostics }`: `ok` is true when the module parses and every import resolves to another zJs module; each diagnostic carries a `severity`, `message`, `line`, and `col`. No JavaScript runs during a check.

# api The ZeroJS public API: zerojs.new/eval, VM run/get/set, sentinels, and version. The package root init.luau re-exports this module.

# parser The JavaScript parser: `parser.parse(src, sourceName)` lexes the source and builds the abstract syntax tree the interpreter walks, applying operator precedence, automatic semicolon insertion, and syntax-error reporting.

# bridge Marshaling between Luau host values and a realm's JavaScript value model. `bridge.toJs(rt, luauValue)` lifts a Luau value into JS; `bridge.toLuau(rt, jsValue)` lowers a JS value back into Luau. Numbers, strings and booleans pass through both ways. Luau `nil` becomes `values.undefined`; `values.undefined` becomes `nil` and `values.null` returns the sentinel itself. A dense integer-keyed Luau table becomes a 0-based JS array; any other plain table becomes a JS object. Luau functions become JS functions (and vice versa), calling back across the boundary with arguments and return values marshaled. Tables carrying a metatable and userdata are opaque host handles, wrapped in a private JS field and unwrapped back to the original on the return trip, so values like AssetRefs survive round trips. Both directions are deep and cycle-safe: a per-call seen-map yields one result container per source container.