API Integration Cheatsheet — The Complete Developer Reference

API Integration is one of the most important skills for modern developers. APIs (Application Programming Interfaces) connect software applications, enabling them to exchange data, trigger actions, and automate workflows.

This API Integration Cheatsheet helps you understand how APIs work, how to connect to them securely, and how to use them in JavaScript, PHP, Python, Node.js, and cURL.

What Is API Integration?

API Integration allows two applications to communicate seamlessly using structured protocols such as HTTP, REST, SOAP, or GraphQL.

For example, when you sign in using Google or fetch live weather data from OpenWeather API — that’s API integration in action.

Core Concepts of API Integration

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HTTP Methods Overview

Example: Simple API Call Using Fetch (JavaScript)

fetch('https://jsonplaceholder.typicode.com/posts')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error('Error:', error));

POST Request with Fetch API

fetch('https://jsonplaceholder.typicode.com/posts', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    title: 'Learn API Integration',
    body: 'This is a demo post',
    userId: 1
  })
})
.then(res => res.json())
.then(data => console.log(data));

API Integration Using Axios (Modern JS Library)

import axios from 'axios';

axios.get('https://jsonplaceholder.typicode.com/users')
  .then(res => console.log(res.data))
  .catch(err => console.error(err));

POST Example:

axios.post('https://api.example.com/login', {
  username: 'admin',
  password: '12345'
})
.then(res => console.log('Token:', res.data.token))
.catch(err => console.error('Login failed:', err));

PHP API Integration Example

<?php
$url = "https://jsonplaceholder.typicode.com/posts";
$data = array("title" => "API Example", "body" => "Hello World", "userId" => 1);
$options = array(
  "http" => array(
    "header"  => "Content-Type: application/json\r\n",
    "method"  => "POST",
    "content" => json_encode($data),
  ),
);
$context  = stream_context_create($options);
$result = file_get_contents($url, false, $context);
echo $result;
?>

Python API Integration Example

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
print(response.json())

POST Example:

import requests

data = {"title": "Python API", "body": "Learning integration", "userId": 10}
response = requests.post("https://jsonplaceholder.typicode.com/posts", json=data)
print(response.json())

Node.js API Integration Example

const fetch = require("node-fetch");

fetch("https://jsonplaceholder.typicode.com/users")
  .then(res => res.json())
  .then(data => console.log(data));

Using cURL for API Testing

curl -X GET https://jsonplaceholder.typicode.com/posts

POST Example:

curl -X POST https://jsonplaceholder.typicode.com/posts \
-H "Content-Type: application/json" \
-d '{"title":"cURL Demo","body":"API Integration via cURL","userId":1}'

API Authentication Techniques

Example (Bearer Token):

fetch("https://api.example.com/data", {
  headers: {
    "Authorization": "Bearer YOUR_ACCESS_TOKEN"
  }
});

Handling JSON Data in APIs

Convert to JSON (JS):

let data = {name: "Alice", age: 22};
console.log(JSON.stringify(data));

Parse JSON:

let response = '{"status":"success"}';
let obj = JSON.parse(response);
console.log(obj.status);

Best Practices for API Integration

✅ Always use HTTPS
✅ Keep your API keys private
✅ Implement rate limiting and caching
✅ Use environment variables for secrets
✅ Log and handle errors gracefully
✅ Test your endpoints with tools like Postman or Insomnia

Common HTTP Response Codes

Popular Public APIs for Practice

Internal Backlinks

• JavaScript Cheatsheet
• Node.js Cheatsheet
• JSON Cheatsheet
• PHP Cheatsheet
• AJAX Cheatsheet

FAQ — API Integration Cheatsheet

Q1: What does API stand for?
API means Application Programming Interface — a bridge that allows apps to communicate.

Q2: What’s the difference between REST and SOAP APIs?
REST uses lightweight JSON and HTTP; SOAP uses XML and heavier protocols.

Q3: How do I test my API calls?
Use tools like Postman, Insomnia, or browser DevTools → Network tab.

Q4: Is API integration difficult?
Not at all! With Fetch or Axios, you can integrate APIs easily using just a few lines of code.

Q5: What is an API key?
An API key is a unique identifier used for authenticating requests to an API.