Convert cURL to JavaScript — Fetch, Axios & Node.js Guide with Code

When inspecting network traffic in Chrome DevTools or reading modern API documentation (Stripe, GitHub, OpenAI), code samples are universally provided as curl commands.

When writing modern client-side React code or backend Node.js microservices, translating those commands into clean fetch() or axios calls is a daily developer task.

This guide provides a complete flag-by-flag mapping.

1. The Core cURL to Fetch Mapping Table

2. Basic GET Request

cURL:

curl "https://api.example.com/v1/items?limit=10&status=active"

Native Fetch (Modern Async/Await):

const url = new URL('https://api.example.com/v1/items');
url.searchParams.set('limit', '10');
url.searchParams.set('status', 'active');

const response = await fetch(url.toString(), {
  method: 'GET',
});

if (!response.ok) {
  throw new Error(`HTTP error! status: ${response.status}`);
}

const data = await response.json();
console.log(data);

Axios:

import axios from 'axios';

const { data } = await axios.get('https://api.example.com/v1/items', {
  params: {
    limit: 10,
    status: 'active',
  },
});
console.log(data);

3. POST Request with JSON Body & Bearer Auth

cURL:

curl -X POST https://api.example.com/v1/orders \
  -H "Authorization: Bearer my_secret_token_123" \
  -H "Content-Type: application/json" \
  -d '{"itemId": "item_987", "quantity": 3}'

Native Fetch:

const response = await fetch('https://api.example.com/v1/orders', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer my_secret_token_123',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    itemId: 'item_987',
    quantity: 3,
  }),
});

if (!response.ok) {
  const errorData = await response.json().catch(() => null);
  throw new Error(errorData?.message || `Request failed with status ${response.status}`);
}

const result = await response.json();
console.log(result);

4. Production Timeout Handling with AbortSignal

In modern JavaScript (Node.js 18+ and all evergreen browsers), never call fetch() without a timeout signal:

try {
  const res = await fetch('https://api.example.com/slow-endpoint', {
    signal: AbortSignal.timeout(4000), // Automatically aborts after 4 seconds
  });
  const data = await res.json();
} catch (err: any) {
  if (err.name === 'TimeoutError') {
    console.error('Request timed out after 4 seconds');
  } else {
    console.error('Network failure:', err);
  }
}