React

React is used in specific parts of the GitLab user interface to enhance functionality. React is a JavaScript library used to build user interfaces. React components are used to construct a UI and they are encapsulated units of code that manage their own state and logic.

React Components

React components are the building blocks of React applications. They are reusable units of code that represent a part of the user interface. They are encapsulated and manage their own state and logic. They allow for building complex user interfaces from smaller, reusable components.

Example

import React from 'react';
          
          function Welcome(props) {
            return <h1>Hello, {props.name}</h1>;
          }
          
          export default Welcome;
          

React Hooks

React Hooks allow us to use features like state and lifecycle methods without writing a class component. They are functions that let you “hook into” React features.

Example

import React, { useState } from 'react';
          
          function Counter() {
            const [count, setCount] = useState(0);
          
            return (
              <div>
                <p>You clicked {count} times</p>
                <button onClick={() => setCount(count + 1)}>Click me</button>
              </div>
            );
          }
          
          export default Counter;
          

State Management

State management is a crucial aspect of React development. It’s the process of storing and updating data that affects the UI.

Example

import React, { useState } from 'react';
          
          function Counter() {
            const [count, setCount] = useState(0);
          
            return (
              <div>
                <p>You clicked {count} times</p>
                <button onClick={() => setCount(count + 1)}>Click me</button>
              </div>
            );
          }
          
          export default Counter;
          

Redux

Redux is a popular state management library that can help manage complex state in React applications. It provides a centralized store for application state, allowing for consistent updates and easy access to data.

Example

import { createStore } from 'redux';
          
          const initialState = { count: 0 };
          
          const reducer = (state = initialState, action) => {
            switch (action.type) {
              case 'INCREMENT':
                return { count: state.count + 1 };
              default:
                return state;
            }
          };
          
          const store = createStore(reducer);
          

React Router

React Router is a library used to manage navigation in React applications. It allows us to create single-page applications with multiple views and seamless transitions between them.

Example

import { BrowserRouter as Router, Routes, Route, Link } from 'react-router-dom';
          
          function App() {
            return (
              <Router>
                <nav>
                  <ul>
                    <li>
                      <Link to="/">Home</Link>
                    </li>
                    <li>
                      <Link to="/about">About</Link>
                    </li>
                  </ul>
                </nav>
          
                <Routes>
                  <Route path="/" element={<Home />} />
                  <Route path="/about" element={<About />} />
                </Routes>
              </Router>
            );
          }
          

React Testing Library

React Testing Library is a library used to write tests for React components. It encourages writing tests that focus on how users interact with the application.

Example

import { render, screen, fireEvent } from '@testing-library/react';
          import Counter from './Counter';
          
          test('renders learn react link', () => {
            render(<Counter />);
            const linkElement = screen.getByText(/learn react/i);
            expect(linkElement).toBeInTheDocument();
          });
          

Note: This outline is based on the context provided. If you have more specific questions about React usage within the GitLab codebase, please provide further context or links.