Run JavaScript in Sandbox API

Execute JavaScript code strings in an isolated, sandboxed Node.js VM environment via REST API. The sandbox has no access to the filesystem, network, or Node.js process — making it safe to run untrusted or user-provided code and return the result.

How it works

POST a JavaScript code string. The API executes it inside a vm.runInNewContext() sandbox with a configurable timeout (default 5 seconds). Returns the return value of the last expression, all console.log output captured as an array, execution time in milliseconds, and any thrown errors.

Use cases

• Run user-submitted JavaScript formulas in a no-code tool or spreadsheet
• Execute transformation logic in an ETL pipeline without deploying code
• Test JavaScript snippets in CI without spinning up a full Node.js environment
• Build a code playground or REPL in a web app without server infrastructure
• Run agent-generated code safely to verify its output before deployment

API Reference

POST https://slopshop.gg/v1/exec-javascript
Authorization: Bearer YOUR_API_KEY
Content-Type: application/json

Input parameters

Example response

{
  "data": {
    "result": 42,
    "console": [],
    "execution_ms": 3
  },
  "meta": {
    "credits_used": 5,
    "engine": "real",
    "ms": 4
  }
}

Examples

Three real-world scenarios showing how developers use Run JavaScript in Sandbox in production.

curl -X POST https://slopshop.gg/v1/exec-javascript \
  -H "Authorization: Bearer $SLOPSHOP_KEY" \
  -H "Content-Type: application/json" \
  -d '{"code": "const data = [1,2,3,4,5]; return data.map(x => x * 2).filter(x => x > 4);"}'

curl -X POST https://slopshop.gg/v1/exec-javascript \
  -H "Authorization: Bearer $SLOPSHOP_KEY" \
  -H "Content-Type: application/json" \
  -d '{"code": "const revenue = 150000; const cost = 87000; return ((revenue - cost) / revenue * 100).toFixed(2) + '%';"}'

curl -X POST https://slopshop.gg/v1/exec-javascript \
  -H "Authorization: Bearer $SLOPSHOP_KEY" \
  -H "Content-Type: application/json" \
  -d '{"code": "function bubbleSort(arr) { for(let i=0;iarr[j+1]) [arr[j],arr[j+1]]=[arr[j+1],arr[j]]; return arr; } return bubbleSort([5,3,8,1,9,2]);"}'

Code examples

curl

curl -X POST https://slopshop.gg/v1/exec-javascript \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"input": "your data here"}'

Python

import requests

response = requests.post(
    "https://slopshop.gg/v1/exec-javascript",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    json={"input": "your data here"}
)
result = response.json()
print(result["data"])

Node.js

const response = await fetch("https://slopshop.gg/v1/exec-javascript", {
  method: "POST",
  headers: {
    "Authorization": "Bearer YOUR_API_KEY",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({ input: "your data here" })
});
const { data } = await response.json();
console.log(data);

CLI

# Install the Slopshop CLI
npm install -g slopshop

# Set your API key
export SLOPSHOP_KEY=your_api_key

# Call exec-javascript
slop exec-javascript '{"input": "your data here"}'

Pricing

Credits are purchased in bundles starting at $1 for 1,000 credits. All compute APIs like this one use 5 credits per call — that's $0.005. See all pricing tiers.

Related APIs in Execute

• Evaluate Math Expression API — Evaluate a complex mathematical expression string including variables, functions (sin, cos, log, sqrt, factorial), and constants (pi, e). Supports unit awareness and returns both numeric result and step-by-step breakdown.
• Run jq Query on JSON API — Apply a jq-compatible filter expression to a JSON input and return the result. Supports field selection, array indexing, pipes, map, select, and common jq functions. No shell execution — pure JS implementation.
• Regex Match All Groups API — Apply a regular expression to a text string and return every match with all capture group values, match positions (start/end indices), and match count. Supports named capture groups. Returns structured results.
• JSONPath Query API — Run a JSONPath expression (e.g. $.store.book[*].author) against a JSON object and return all matching values. Like XPath for JSON. Supports recursive descent, wildcards, filters, and array slices.
• Render Handlebars Template API — Render a Handlebars template string with a provided data object. Supports {{variable}}, {{#if}}, {{#each}}, {{#with}}, partials passed as extra argument, and custom helpers: eq, gt, lt, and, or, not.

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