Axios — Complete Guide

Axios — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of React.js Tutorial on Toolliyo Academy.

8 min read Updated 7/8/2026

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React.js Tutorial · Lesson 37 of 100

Axios

Beginner ✓ → Intermediate → Advanced → Professional

Intermediate · 2 — Build apps · ~14 min read · Module 4: Routing & Data

Introduction

You know the basics now. Here we use Axios in real app situations — forms, pages, and data. Still plain language, just a bit more depth. Axios is an HTTP client library. It automatically parses JSON, has interceptors for auth headers, and throws on 4xx/5xx status codes. Teams use one axios instance with baseURL and auth so every API call does not repeat the same setup.

Routing is how a single React app feels like many pages. Users expect URLs like /cart and /checkout — Router makes that work.

When will you use this?

Add routing when your app has more than one screen and URLs should be bookmarkable.

Multi-page apps like dashboards use React Router — /settings, /profile, /orders.
E-commerce sites route /product/123 to a product detail component.

Real-world: HDFC API client with interceptors

Banking SPA uses axios instance with base URL, JWT injection, and global 401 handler that redirects to login.

Production-style code

import axios from 'axios';

export const bankingApi = axios.create({
  baseURL: 'https://api.hdfc.example/v1',
  timeout: 15000
});

bankingApi.interceptors.request.use(config => {
  const token = sessionStorage.getItem('accessToken');
  if (token) config.headers.Authorization = `Bearer ${token}`;
  return config;
});

bankingApi.interceptors.response.use(
  res => res,
  err => {
    if (err.response?.status === 401) window.location.href = '/login';
    return Promise.reject(err);
  }
);

What happens in production: One configured client serves accounts, transfers, and cards — DRY auth and error handling across 40+ endpoints.

Lesson example (start here)

Copy this smaller example first. Once it works, compare it with the real-world code above.

import axios from 'axios';

const api = axios.create({ baseURL: '/api' });

api.interceptors.request.use(config => {
  const token = localStorage.getItem('token');
  if (token) config.headers.Authorization = `Bearer ${token}`;
  return config;
});

const { data } = await api.get('/users');

Line-by-line walkthrough

Code	What it means
`import axios from 'axios';`	Imports code from React or another file so you can use it here.
`const api = axios.create({ baseURL: '/api' });`	Calls an API to load or save data from a server.
`api.interceptors.request.use(config => {`	Defines a function — often a component or event handler.
`const token = localStorage.getItem('token');`	Part of the Axios example — read it together with the lines before and after.
if (token) config.headers.Authorization = `Bearer ${token}`;	Part of the Axios example — read it together with the lines before and after.
`return config;`	Sends UI or a value back to whoever called this function.
`});`	Closes a block started by { or ( above.
`const { data } = await api.get('/users');`	Part of the Axios example — read it together with the lines before and after.

How it works (big picture)

create sets base URL once.
Interceptor runs before each request.
await api.get throws if server returns error status.

Do this on your computer

npm install axios
Create api.js with axios.create.
Import api in components instead of raw fetch.
Read the real-world section and name which part of the app uses this topic.
Run the example locally and confirm the same behavior in the browser.
Change one value in the example (text, initial state, or URL) and predict what will happen before you save.

Experiments — try changing this

Change text or labels in the example and save — watch the browser update.
Break the code on purpose (remove a bracket), read the error message, then fix it.
Open React DevTools (browser extension) while running Axios and inspect component props/state.

Remember

One shared axios instance per app. Interceptors for auth and errors. async/await with try/catch.

Common questions

Does axios work in Node?

Yes — same API for React and Express backends.

How long should I spend on Axios?

Until you can explain it in your own words and run the example without looking at the answer. Beginners often need 30–60 minutes per new hook or routing topic; setup lessons may take one afternoon.

What if I get stuck on Axios?

Re-read the line-by-line walkthrough, check the browser console for red errors, and compare your code character-by-character with the example. Search the exact error text — someone else had it too.

Where is Axios used in real jobs?

See the real-world section above — the same pattern appears in LMS, banking, e-commerce, and SaaS products. Interviewers ask you to explain it using one concrete example from your project or this lesson.

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