Definition: What is Converting cURL to Fetch/Axios?
Converting cURL to Fetch/Axios is the process of translating cURL command-line HTTP requests into equivalent JavaScript code using the Fetch API or Axios library. cURL is a command-line tool for making HTTP requests, while Fetch and Axios are JavaScript APIs for making HTTP requests in browsers and Node.js.
This conversion involves translating cURL flags and options into JavaScript equivalents: HTTP methods (-X), headers (-H), request body (-d, --data-raw), authentication (-u, -H Authorization), and other options. The goal is to create JavaScript code that performs the same HTTP request as the original cURL command.
Converting cURL to JavaScript is essential when you need to use API endpoints in web applications, test APIs in browser environments, or integrate command-line API examples into JavaScript code. Many developers start with cURL examples from API documentation and need to convert them to JavaScript for their applications.
Key Point: Converting cURL to Fetch/Axios translates command-line HTTP requests into browser-compatible JavaScript code. This enables you to use API endpoints in web applications, test APIs in JavaScript environments, and integrate command-line examples into your code.
What: Understanding cURL to JavaScript Conversion
Converting cURL to Fetch/Axios involves several components:
HTTP Methods
cURL uses -X flag to specify HTTP methods (GET, POST, PUT, DELETE, etc.). In Fetch/Axios, methods are specified as properties: method: "POST" in Fetch, or axios.post() in Axios.
Example: curl -X POST becomes fetch(url, { method: "POST" })
Headers
cURL uses -H flag for headers. In Fetch/Axios, headers are objects: headers: { "Content-Type": "application/json" }. Multiple -H flags become multiple header properties.
Example: -H "Content-Type: application/json" becomes headers: { "Content-Type": "application/json" }
Request Body
cURL uses -d or --data-raw for request body. In Fetch, use body property with JSON.stringify() for JSON. In Axios, use data property (auto-serialized).
Example: -d '{"key":"value"}' becomes body: JSON.stringify({key: "value"})
Authentication
cURL uses -u for Basic auth or -H "Authorization: Bearer token" for tokens. In Fetch/Axios, use headers: { Authorization: "Basic " + btoa("user:pass") } or headers: { Authorization: "Bearer token" }.
Authentication is converted to Authorization header
Important: Understanding cURL flags and their JavaScript equivalents is key to accurate conversion. Each cURL option has a corresponding JavaScript property or method. Online converters automate this, but manual conversion helps you understand the mapping.
When: When to Convert cURL to Fetch/Axios
You should convert cURL to Fetch/Axios in these situations:
API Documentation Examples
When API documentation provides cURL examples, you need to convert them to JavaScript for use in web applications. Most API docs include cURL examples that need translation to your JavaScript framework.
Browser-Based Applications
When building web applications that need to make HTTP requests, you must use Fetch or Axios instead of cURL. cURL is command-line only, while Fetch/Axios work in browsers and Node.js.
Testing and Debugging
When testing APIs in browser DevTools or JavaScript environments, converting cURL to Fetch/Axios allows you to test endpoints directly in the browser console or your application code.
Code Integration
When integrating API endpoints into existing JavaScript applications, converting cURL examples to Fetch/Axios enables seamless integration with your codebase and framework.
Common Scenario: Converting cURL to Fetch/Axios is most common when working with API documentation, building web applications, or testing APIs in JavaScript environments. Most modern APIs provide cURL examples that need JavaScript conversion.
How To: Convert cURL to Fetch/Axios
Follow these methods to convert cURL to Fetch/Axios:
Method 1: Using Online Converters (Automatic)
Use online tools for automatic conversion:
Popular Online Tools
curlconverter.com
Paste your cURL command and get Fetch, Axios, or other language code. Supports all cURL features including authentication, headers, and data.
Best for: Quick automatic conversion with multiple output formats
Postman (Import cURL)
Import cURL commands into Postman, then generate Fetch/Axios code. Great for testing and code generation.
Best for: Testing APIs and generating code snippets
Browser Extensions
Extensions like "cURL to Code" can convert cURL commands directly in your browser. Useful for quick conversions while browsing API docs.
Best for: Quick conversions while reading documentation
Method 2: Manual Conversion to Fetch
Convert cURL manually to Fetch API:
Basic GET Request
// cURL
curl https://api.example.com/users
// Fetch
fetch('https://api.example.com/users')
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));
// Or with async/await
async function getUsers() {
try {
const response = await fetch('https://api.example.com/users');
const data = await response.json();
return data;
} catch (error) {
console.error('Error:', error);
}
}POST Request with JSON
// cURL
curl -X POST https://api.example.com/users \
-H "Content-Type: application/json" \
-d '{"name":"John","email":"john@example.com"}'
// Fetch
fetch('https://api.example.com/users', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
name: 'John',
email: 'john@example.com'
})
})
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));With Authentication
// cURL with Basic Auth
curl -u username:password https://api.example.com/protected
// Fetch with Basic Auth
const credentials = btoa('username:password');
fetch('https://api.example.com/protected', {
headers: {
'Authorization': 'Basic ' + credentials
}
})
.then(response => response.json())
.then(data => console.log(data));
// cURL with Bearer Token
curl -H "Authorization: Bearer token123" https://api.example.com/protected
// Fetch with Bearer Token
fetch('https://api.example.com/protected', {
headers: {
'Authorization': 'Bearer token123'
}
})
.then(response => response.json())
.then(data => console.log(data));Method 3: Manual Conversion to Axios
Convert cURL manually to Axios:
Basic GET Request
// cURL
curl https://api.example.com/users
// Axios
import axios from 'axios';
axios.get('https://api.example.com/users')
.then(response => console.log(response.data))
.catch(error => console.error('Error:', error));
// Or with async/await
async function getUsers() {
try {
const response = await axios.get('https://api.example.com/users');
return response.data;
} catch (error) {
console.error('Error:', error);
}
}POST Request with JSON
// cURL
curl -X POST https://api.example.com/users \
-H "Content-Type: application/json" \
-d '{"name":"John","email":"john@example.com"}'
// Axios (auto-serializes JSON)
axios.post('https://api.example.com/users', {
name: 'John',
email: 'john@example.com'
})
.then(response => console.log(response.data))
.catch(error => console.error('Error:', error));
// Or with explicit headers
axios.post('https://api.example.com/users', {
name: 'John',
email: 'john@example.com'
}, {
headers: {
'Content-Type': 'application/json'
}
});With Authentication
// cURL with Basic Auth
curl -u username:password https://api.example.com/protected
// Axios with Basic Auth
import axios from 'axios';
axios.get('https://api.example.com/protected', {
auth: {
username: 'username',
password: 'password'
}
})
.then(response => console.log(response.data));
// cURL with Bearer Token
curl -H "Authorization: Bearer token123" https://api.example.com/protected
// Axios with Bearer Token
axios.get('https://api.example.com/protected', {
headers: {
'Authorization': 'Bearer token123'
}
})
.then(response => console.log(response.data));Method 4: Common cURL to JavaScript Mappings
Quick Reference Table
| cURL Flag | Fetch Equivalent | Axios Equivalent |
|---|---|---|
| -X POST | method: 'POST' | axios.post() |
| -H "Header: Value" | headers: { "Header": "Value" } | headers: { "Header": "Value" } |
| -d '{"key":"value"}' | body: JSON.stringify({key: "value"}) | data: {key: "value"} |
| -u user:pass | headers: { Authorization: "Basic " + btoa("user:pass") } | auth: { username: "user", password: "pass" } |
| --data-raw | body: rawString | data: rawString |
Best Practice: Use online converters for quick conversions, but understand manual conversion for debugging and customization. Always test converted code, handle errors properly, and validate that authentication and headers are correctly translated.
Why: Why Convert cURL to Fetch/Axios
Converting cURL to Fetch/Axios is important for several reasons:
Browser Compatibility
cURL is a command-line tool that doesn't work in browsers. Fetch and Axios are JavaScript APIs that work in browsers and Node.js, enabling you to make HTTP requests from web applications. Converting cURL allows browser-based API integration.
Code Integration
Most API documentation provides cURL examples. Converting these to Fetch/Axios enables seamless integration into JavaScript applications, React components, and Node.js backends. This bridges the gap between documentation and implementation.
Developer Experience
Fetch and Axios provide better developer experience with promises, async/await, automatic JSON parsing, and error handling. Converting cURL improves code readability and maintainability in JavaScript projects.
Testing and Debugging
Converting cURL to Fetch/Axios allows testing APIs directly in browser DevTools, React applications, or Node.js scripts. This enables faster debugging and testing compared to switching between terminal and browser.
Important: Converting cURL to Fetch/Axios is essential for modern web development. It enables browser-based API integration, improves developer experience, and allows seamless use of API documentation examples in JavaScript applications.
Frequently Asked Questions
How do I convert cURL to Fetch automatically?
Use online tools like curlconverter.com, or manually convert: Replace curl with fetch(), convert -X POST to method: "POST", convert -H headers to headers object, convert -d data to body, and convert --data-raw to JSON.stringify(). Most online converters handle this automatically.
How do I convert cURL to Axios?
Use online converters or manually: Replace curl with axios, convert -X method to method property, convert -H headers to headers object, convert -d data to data property, and convert authentication to auth or headers. Axios automatically handles JSON serialization.
What is the best tool to convert cURL to JavaScript?
Online tools like curlconverter.com, postman.com (import cURL), and various browser extensions can convert cURL to Fetch or Axios automatically. For manual conversion, understand cURL flags: -X for method, -H for headers, -d for data, --data-raw for raw JSON.
Can I convert cURL with authentication to Fetch?
Yes, convert Basic auth: -u user:pass becomes headers: { Authorization: "Basic " + btoa("user:pass") }. Convert Bearer token: -H "Authorization: Bearer token" becomes headers: { Authorization: "Bearer token" }. Convert API keys: -H "X-API-Key: key" becomes headers: { "X-API-Key": "key" }.
How do I handle cURL POST data in Fetch/Axios?
For JSON data: Convert -d '{"key":"value"}' to body: JSON.stringify({key: "value"}) with Content-Type: application/json. For form data: Convert -d "key=value" to body: new URLSearchParams({key: "value"}) with Content-Type: application/x-www-form-urlencoded. For files: Use FormData object.