# TypeScript

`secure-exec/typescript` exports the same `execute` and `evaluate` as the main
entry point, plus `check`.

secure-exec/examples/typescript/src/index.ts:

```ts
import { check, evaluate } from "secure-exec/typescript";

// Running TypeScript strips types without checking them, so type-check an
// agent's generated code first and feed the diagnostics back to it.
const generated = `([5, 10, "27"] as number[]).reduce((a, b) => a + b, 0)`;

const checked = await check(generated, { filePath: "generated.ts" });
for (const diagnostic of checked.diagnostics) {
	console.log(
		`${diagnostic.category} TS${diagnostic.code}: ${diagnostic.message}`,
	);
}

const fixed = generated.replace(`"27"`, "27");
const recheck = await check(fixed, { filePath: "generated.ts" });
if (recheck.outcome === "succeeded" && !recheck.hasErrors) {
	const result = await evaluate<number>(fixed);
	console.log(result.outcome === "succeeded" ? result.value : result.error); // 42
}
```

## Running strips types

`execute` and `evaluate` transpile TypeScript and run it. They do **not** type
check, so code with type errors still runs. This keeps the hot path fast.

## Checking runs the real compiler

`check` runs the TypeScript compiler inside the VM and returns structured
diagnostics without running your code. Each diagnostic has a `code`,
`category`, `message`, and, when known, a `filePath`, `line`, and `column`.

`filePath` only labels the source in diagnostics. It is never read from disk.
Pass `compilerOptions` or `tsconfigPath` to change compiler settings.

## Check a project

A project lives in a VM's filesystem, so type-check it on a
[VM](/secure-exec/docs/vms). `vm.typescript.checkProject()` checks the project in
the working directory using its `tsconfig.json`, and `vm.typescript` has the
same `execute`, `evaluate`, `executeFile`, and `check` as this entry point.

Feeding diagnostics back to a model is the cheapest way to fix generated code.
See [Agent Code Tool](/secure-exec/docs/use-cases/agent-code-tool).