Can I use document or fetch?

No. The sandbox has no DOM, network or browser APIs. To work with web pages, use the online HTML editor.

Does it check TypeScript types?

No. Types are stripped and the code runs as JavaScript, so only syntax errors are shown.

Which syntax is supported?

Modern JavaScript, including let/const, arrow functions, classes, destructuring, template literals and optional chaining.

Online JavaScript & TypeScript Compiler

Run JavaScript and TypeScript online with modern ES2020+ syntax. See console.log output instantly in an isolated sandbox. Free, no sign-up.

Ctrl/⌘ + Enter to run

main.js

const orders = [
  { id: 1, customer: "Ana", total: 42.5, paid: true },
  { id: 2, customer: "Ben", total: 18, paid: false },
  { id: 3, customer: "Ana", total: 27.25, paid: true }
];

class Cart {
  #items = [];
  add(name, price) {
    this.#items.push({ name, price });
    return this;
  }
  get total() {
    return this.#items.reduce((sum, item) => sum + item.price, 0);
  }
}

const wait = ms => new Promise(resolve => setTimeout(resolve, ms));

async function main() {
  const paid = orders.filter(order => order.paid);
  const spent = paid.reduce((sums, order) => {
    sums[order.customer] = (sums[order.customer] ?? 0) + order.total;
    return sums;
  }, {});
  console.log("Paid orders:", paid.map(order => order.id).join(", "));
  console.log("Spent per customer:", spent);

await wait(100);
  const cart = new Cart().add("Pen", 1.5).add("Notebook", 3.25);
  console.log(`Cart total: ${cart.total.toFixed(2)}`);

for (const { id, customer, total } of orders)
    console.log(`#${id}`.padEnd(4), customer.padEnd(5), total.toFixed(2).padStart(6));
}

main();

Output

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JavaScript

Code runs locally in your browser; it is not uploaded.

Format references

Tool page updated: 2026-10-22

Output

Guide and example

Related tools

Format references