面试题与答案

Front-end is client-side development, dealing with user interfaces, while back-end is server-side development, handling server operations and databases.

AJAX (Asynchronous JavaScript and XML) allows web pages to update content asynchronously by making background requests to the server without reloading the entire page.

A package manager helps manage and install third-party libraries, tools, and dependencies, streamlining the development process.

Promises are used to handle asynchronous operations in JavaScript, providing a cleaner and more readable way to manage callbacks.

Responsive web design ensures that a web application or site adapts to different screen sizes and devices, providing an optimal user experience.

Git allows developers to track changes, collaborate on projects, and manage different versions of code, providing a robust version control system.

The 'use strict' statement enables strict mode in JavaScript, catching common coding errors and preventing the use of certain error-prone features.

In JavaScript, 'this' refers to the current execution context. Its value depends on how a function is called and is often used within object methods.

HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the web. It defines how messages are formatted and transmitted, enabling the exchange of information between a client and a server.

A CDN is a network of distributed servers that deliver web content to users based on their geographic location, reducing latency and improving page load times.

Cookies are small pieces of data sent from a server and stored in the user's browser, while local storage is a larger storage area for key-value pairs that persists even when the browser is closed.

A stateless protocol does not store information about the state of communication between requests. An example is HTTP, where each request is independent of previous requests.

Async/await is a syntax for working with asynchronous code in JavaScript, making it more readable and allowing developers to write asynchronous code that resembles synchronous code.

The 'useEffect' hook in React.js is used for side effects in functional components, such as data fetching, subscriptions, or manually changing the DOM.

The 'defer' attribute in the 'script' tag tells the browser to defer the execution of the script until after the HTML document is fully parsed. This can improve page load performance.

The 'map' function in JavaScript is used to transform each element of an array and create a new array with the results. Example: `const numbers = [1, 2, 3]; const doubled = numbers.map(num => num * 2);`