This time I bring you the latest front-end interview questions in 2018. We know that interviews are an indispensable part of front-end work. This time, the common front-end interview questions are sorted and summarized to help you get through the front-end process. The interview is a big challenge. Let’s take a look.
[Related recommendations: Front-end interview questions (2020)]
1. Please name three ways to reduce page loading time. (Loading time refers to perceived time or actual loading time)
1. Reduce HTTP requests;
2. Merge and compress Js/css files;
3. Use cache manifest;
4. Turn on gzip on the server side;
5. Using CDN, users can obtain the resources they need nearby, the access speed is guaranteed, and the stability is guaranteed
6. Put external JS and CSS aside
7. Operate the DOM as little as possible. Some DOM that require repeated operations can be placed in variables
2. Please describe pseudo-elements (pseudo-elements) and their uses.
Pseudo-classes are used to select information that does not exist in the DOM tree and are not easily found by conventional selectors:hover :active :focus :link
Pseudo-elements are used to apply certain special effects Add to the selector; such as: :before ::after
Pseudo elements are used to express non-text and decorative things, which is conducive to HTMLsemantic;
3. Do you have experience with retina screen compatibility? If so, what technology is used where?
Taobao's lib-flexible library;
4. Why should you use translate() instead of absolute position, or vice versa? Why?
In terms of animation, transform can allow the GPU to participate in calculations, resulting in higher FPS; absolute minimum animation unit is 1px, and transform can be smaller, making the animation smoother.
From other perspectives In other words, absolute must have a relative parent box;
5. How do you organize your code? Should I use the module pattern or the classic inheritance method? (This is the answer after Baidu)
Internal: module mode;
External: inheritance
6. Explanation of function foo() {} and var foo = function() {} The difference in usage
1. The function declaration must have a function name, 2. It can be called anywhere, that is, there is variable promotion
3.Function expression The two names before and after can be the same or different; 4. The name after the function expression can be omitted;
5. The name after the expression can only be used inside the function; 6. The function can only be used after it is declared Call
7. Please explain how JSONP works and why it is not true Ajax.
json is a data format; jsonp is a method of data calling;
1. Take advantage of the fact that the script tag has no cross-domain restrictions, create a script tag in the script, and the address points to Third-party API, such as
(the src attribute is not subject to cross-domain restrictions)
2. Provide a callback function to receive data; the data generated by the third party is a package of json data, in the form of callback({"name":"hax","gender":"Male"} ), the callback function can pass callback=fn
3 through the URL parameter. In this way, the browser will call the callback function and pass the parsed json object as a parameter. The script of this website can process the incoming data in the callback function; ajax essentially obtains server information through You have mastered the case method. For more exciting information, please pay attention to other related articles on the PHP Chinese website!
Related reading:
2018 latest front-end interview questions four2018 latest front-end interview questions three2018 latest front-end interview questions two2018 latest front-end interview questions oneThe above is the detailed content of 2018 latest front-end interview questions five. For more information, please follow other related articles on the PHP Chinese website!

The differences in performance and efficiency between Python and JavaScript are mainly reflected in: 1) As an interpreted language, Python runs slowly but has high development efficiency and is suitable for rapid prototype development; 2) JavaScript is limited to single thread in the browser, but multi-threading and asynchronous I/O can be used to improve performance in Node.js, and both have advantages in actual projects.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

Atom editor mac version download
The most popular open source editor

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

Zend Studio 13.0.1
Powerful PHP integrated development environment

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
