@tscircuit/eval

Evaluate code in a full tscircuit runtime environment, including Sucrase
transpilation and execution, so you just need to send the code to be executed
with automatic handling of imports from @tsci/*

Contributor Getting Started Video · NPM Package

The circuit object from @tscircuit/core is already exposed on the global
scope. All imports from @tsci/* are automatically handled.

Usage Options

$3

Quickly run tscircuit code in the main thread. You can also supply a virtual
filesystem to run multiple files.

``tsx
import { runTscircuitCode } from "@tscircuit/eval"

const circuitJson = await runTscircuitCode(
export default () => (

)
)

// You've got Circuit JSON!
console.log(circuitJson)
`

$3

`tsx
import { createCircuitWebWorker } from "@tscircuit/eval"

const circuitWebWorker = createCircuitWebWorker()

await circuitWebWorker.execute(
import { RedLed } from "@tsci/seveibar.red-led"

circuit.add(



)
)

await circuitWebWorker.renderUntilSettled()

const circuitJson = await circuitWebWorker.getCircuitJson()
`

$3

For simple cases where you don't need web worker isolation, you can use CircuitRunner directly in the main thread:

`tsx
import { CircuitRunner } from "@tscircuit/eval"

const circuitRunner = new CircuitRunner()

await circuitRunner.execute(
import { RedLed } from "@tsci/seveibar.red-led"

circuit.add(



))

await circuitRunner.renderUntilSettled()

const circuitJson = await circuitRunner.getCircuitJson()
// Validate circuit elements
const led = circuitJson.find((el) => el.name === "LED1")
`

$3

You can also execute code using a virtual filesystem, which is useful when you have multiple files or components:

`tsx
import { createCircuitWebWorker } from "@tscircuit/eval"

const circuitWebWorker = createCircuitWebWorker()

await circuitWebWorker.executeWithFsMap({
fsMap: {
"entrypoint.tsx":
import { MyLed } from "./myled.tsx"

circuit.add(



)
,
"myled.tsx":
import { RedLed } from "@tsci/seveibar.red-led"

export const MyLed = ({ name }) => {
return
}
,
},
entrypoint: "entrypoint.tsx",
})

await circuitWebWorker.renderUntilSettled()

const circuitJson = await circuitWebWorker.getCircuitJson()
`

$3

If you want to quickly run a published tscircuit module by its name (e.g., from the tscircuit registry), you can use runTscircuitModule. This function handles the import and execution for you.

`tsx
import { runTscircuitModule } from "@tscircuit/eval"

// Run a module by its full name
const circuitJson = await runTscircuitModule("@tsci/seveibar.usb-c-flashlight")

// Or use a shorthand (will be prefixed with "@tsci/")
const circuitJsonShorthand = await runTscircuitModule("seveibar/usb-c-flashlight")

console.log(circuitJson)

// You can also pass props to the main component of the module:
const circuitJsonWithProps = await runTscircuitModule("@tsci/seveibar.key", {
props: {
name: "MyCustomKey",
},
})

console.log(circuitJsonWithProps) // The root component will have the name "MyCustomKey"
`

When to Use Which Approach

CircuitRunner (Direct Execution)

- ✅ Simple debugging
- ✅ No worker setup required
- ❌ Blocks main thread
- ❌ No isolation from host environment

CircuitWebWorker (Web Worker)

- ✅ Non-blocking execution
- ✅ Isolated environment
- ✅ Better for production use
- ❌ More complex setup
- ❌ Comlink overhead for communication

Why use a web worker?

tscircuit can block the ui thread in a browser. In addition, tscircuit sometimes
freezes during the render loop due to autorouting or other computationally
intensive operations. Executing tscircuit code in a web worker allows the ui
to display the rendering process without freezing, and stop rendering if it
goes on for too long.

Execution Implementation

1. The execution code is scanned for imports, these imports are then loaded
via fetch from the CDN and added to a global import map.
2. The code is transpiled. Imports/requires automatically check the import map.
3. The transpiled code is executed with a circuit object added to the global
scope.
4. When a user calls circuitWebWorker.renderUntilSettled(), the web worker
the webworker runs circuit.renderUntilSettled()`