# Safe JavaScript Runner for Workflows (isolated V8 sandbox) (`andrew_babo/flow-code-runner`) Actor

Run your own JavaScript over up to 1,000 JSON records per run in an isolated V8 sandbox: no network, no require, no env vars, per-record timeout and memory limits, console.log captured. For scoring, cleaning, dedupe and routing in workflows.

- **URL**: https://apify.com/andrew_babo/flow-code-runner.md
- **Developed by:** [Andrew Babo](https://apify.com/andrew_babo) (community)
- **Categories:** Developer tools, Automation
- **Stats:** 6 total users, 5 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

Pay per usage

This Actor is paid per platform usage. The Actor is free to use, and you only pay for the Apify platform usage, which gets cheaper the higher subscription plan you have.

Learn more: https://docs.apify.com/actors/running/actors-in-store.md#pay-per-usage

## What's an Apify Actor?

An Actor is a serverless cloud program that runs on the Apify platform. It has two run modes.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.

Apify vocabulary and the platform model are defined once, in the agent quickstart at https://apify.com/agents.md.

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For examples already wired to this Actor's own input schema, see the [API](#api) section below.

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).

# README

## Safe JavaScript Runner for Workflows

Run **your own JavaScript function** over a batch of JSON records inside an **isolated V8 sandbox** — the same way workflow tools run their "Code" step on a separate worker.

- **Isolated**: every run gets a fresh V8 isolate (isolated-vm). No `process`, `require`, `import`, `fetch`, timers or environment variables. The sandbox process is started with an empty environment.
- **Per-record limits**: timeout per record (default 1 s, max 5 s), 128 MB memory per isolate, 32 KB output per record, 200 log lines.
- **One bad record never breaks the batch**: syntax errors, exceptions, timeouts and memory blow-ups are reported per record with a code and the line number.
- **Two modes**: `per_item` (function runs once per record) and `all_items` (function receives all records — dedupe, ranking, cross-record rules).

### Input

```json
{
  "code": "const size = Number(item.employee_count ?? 0);\nreturn { score: size >= 50 ? 80 : 30, keep: size >= 10 };",
  "mode": "per_item",
  "items": [{ "id": "r1", "company": "Acme", "employee_count": 120 }],
  "limits": { "perItemMs": 1000 }
}
```

### Output

One dataset item per input record, in input order:

```json
{ "id": "r1", "ok": true, "output": { "score": 80, "keep": true }, "error": null, "logs": [], "ms": 1 }
```

Failed records carry `error: { code, message, line }` where `code` is one of
`code.syntax`, `code.runtime`, `code.timeout`, `code.memory`, `code.output_invalid`,
`code.output_too_large`, `code.missing_output`, `code.batch_timeout`, `code.runner_crash`, `code.input_invalid`.

A run summary (`total`, `ok`, `failed`, `compileError`, `durationMs`) is stored in the default key-value store under `OUTPUT`.

# Actor input Schema

## `code` (type: `string`):

Body of an async function. In per_item mode it receives `item` and must return an object of output fields. In all_items mode it receives `items` and must return an array of { id, ...fields }. console.log is captured. No network, no require, no process.

## `mode` (type: `string`):

per_item: the function runs once per record. all_items: the function runs once with every record (dedupe, ranking).

## `items` (type: `array`):

Up to 1,000 JSON objects, each with a unique string `id`.

## `limits` (type: `object`):

Optional: perItemMs (10–5000, default 1000), allItemsMs (100–60000), batchMs (1000–240000).

## `contractVersion` (type: `integer`):

Input/output contract version expected by the caller (current: 1).

## Actor input object example

```json
{
  "code": "const size = Number(item.employee_count ?? 0);\nreturn { score: size >= 50 ? 80 : 30 };",
  "mode": "per_item",
  "items": [
    {
      "id": "r1",
      "company": "Acme",
      "employee_count": 120
    }
  ],
  "limits": {
    "perItemMs": 1000
  },
  "contractVersion": 1
}
```

# Actor output Schema

## `results` (type: `string`):

Dataset rows in input order: id, ok, output fields, error { code, message, line }, captured console logs, duration.

## `summary` (type: `string`):

Totals, compile error (if any) and duration.

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {
    "code": `const size = Number(item.employee_count ?? 0);
return { score: size >= 50 ? 80 : 30 };`,
    "items": [
        {
            "id": "r1",
            "company": "Acme",
            "employee_count": 120
        }
    ],
    "limits": {
        "perItemMs": 1000
    }
};

// Run the Actor and wait for it to finish
const run = await client.actor("andrew_babo/flow-code-runner").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = {
    "code": """const size = Number(item.employee_count ?? 0);
return { score: size >= 50 ? 80 : 30 };""",
    "items": [{
            "id": "r1",
            "company": "Acme",
            "employee_count": 120,
        }],
    "limits": { "perItemMs": 1000 },
}

# Run the Actor and wait for it to finish
run = client.actor("andrew_babo/flow-code-runner").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print(f"💾 Check your data here: https://console.apify.com/storage/datasets/{run.default_dataset_id}")
for item in client.dataset(run.default_dataset_id).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{
  "code": "const size = Number(item.employee_count ?? 0);\\nreturn { score: size >= 50 ? 80 : 30 };",
  "items": [
    {
      "id": "r1",
      "company": "Acme",
      "employee_count": 120
    }
  ],
  "limits": {
    "perItemMs": 1000
  }
}' |
apify call andrew_babo/flow-code-runner --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,andrew_babo/flow-code-runner"
        }
    }
}
```

The hosted server signs you in with OAuth on first connect, so no API token belongs in this config. Clients without OAuth support can send an `Authorization: Bearer <APIFY_API_TOKEN>` header instead, using a token from API & Integrations in Apify Console (https://console.apify.com/settings/integrations).

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/PdhD2d9fLchOtnkUa/builds/xVosyE5vMXKea0gYK/openapi.json