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This article mainly explains "how to understand the three elements of web front-end". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to understand the three elements of web front-end".

Internet: a network formed by a number of electronic computers connected to each other through a network.

At present, the world's largest Internet made up of the largest number of electronic computers is called the Internet (Internet). The main applications provided are the World wide Web (WWW), file transfer (FTP), e-mail (E-mail), remote login (Telnet) and so on.

It can be said that the World wide Web is one of the most popular applications in the Internet, which mainly provides us with web browsing services, and what we usually watch on the Internet through a browser is the content of the World wide Web.

Hypertext transfer: hypertext transfer Protocol (HTTP,HyperText Transfer Protocol) is one of the most widely used network transmission protocols on the Internet. All WWW files must comply with this standard. HTTP was originally designed to provide a way to publish and receive HTML pages.

HTML: hypertext markup language. HTML is not a programming language, but a markup language (markup language), which is necessary for web page making. "Hypertext" means that a page can contain pictures, links, even music, programs and other non-text elements. The structure of hypertext markup language (or hypertext tag language) includes a "header" part and a "body" part, wherein the "header" part provides information about the web page, and the "body" part provides the specific content of the web page.

What is the relationship between html,css,php: html is the foundation of a web page. It is an essential part of a web page. Css is the style of html. Without the css style, the whole page is basically not beautiful at all, it's just a stack of tags. Because of the css style, the website is colorful.

Php is a server-side dynamic language. Without php, the whole page is just a static page. Only for people to browse, can not achieve other functions. Because the server-side language php is eventually compiled into client-side html.

The relationship between javaScript and HTML, web page foreground is divided into three levels of content, style, behavior this is the latest elements of web design, W3C standard requires content to be expressed in html, style defined by css, behavior controlled by script, the function of html is basically to cut a whole thing into small pieces, mark it if necessary (such as id,class)

In order to make it easy for css and scripts to reference and control the corresponding content, css queues these small pieces of content, specifying who stands where and how. The script is to make those small pieces of content do things. For example, in the picture rotation of the page, the script controls the css attribute of the corresponding element to achieve the purpose of switching.

At present, the most common script used in the front desk of the web page is javascript. Is an implementation of the ecma standard. All kinds of browsers can support it.

1. What is HTML (Hypertext markup language Hyper Text Markup Language)? HTML is a language used to describe web pages.

Markup languages that can contain not only text, but also pictures, links, and even non-text elements such as music and programs (shown to users, not too monotonous, css)

2. CSS (cascading stylesheet Cascading Style Sheets). The style defines how HTML elements are displayed. The syntax is: selector {property:value} (selector {attribute: value})

Is a computer language used to express HTML, which can make HTML pages more beautiful. (it is not enough to show users beautiful light, users should also be able to manipulate HTML pages dynamically, that is, the interaction between browsers and users can not only browse the content in html, but also manipulate html pages, JavaScript).

3 、 JavaScript

Is a scripting language whose source code does not need to be compiled before being sent to the client to run, but sends the character code in text format to the browser to be interpreted and run by the browser. Used to add dynamic functions and interactive behavior to HTML pages. It is an interpretive scripting language (no precompilation).

For a web page, HTML defines the structure of the web page, CSS describes what the web page looks like, and JavaScript settings.

There are two ways of translation, one is compilation and the other is interpretation.

1) compilation: the operation of the Java language is compiled first, but the compilation of the JAVA language is not directly compiled into a language that the computer can recognize, but into a class file recognized by the JAVA virtual function.

JAVA language is a typical compiled programming language, although it is not compiled into a language that can be directly recognized by the computer, but the principle is roughly the same as that of other high-level programming languages that use compilation as translation.

The most obvious: Cmax Cure codes, which can be compiled into binary code and exist as an executable file (exe file)

It is compiled first and then run, and it is compiled and run everywhere at once, which is very efficient. (you only need to compile once the first time you run)

2) explanation: programs of interpretive scripting languages do not need to be compiled, and interpretive scripting languages are translated only when the program is run.

Interpretive scripting languages have special interpreters to interpret, but they need to be translated every time, which is relatively inefficient. JavaScript is an interpretive scripting language.

JavaScript also has its own special interpreter, the JavaScript engine, which exists on the browser side as part of the browser.

In a word: html (Hypertext markup language), css (cascading style sheets) and JavaScript scripting language cooperate and complement each other on the browser side to form a more mature front-end interface.

URI = Universal Resource Identifier uniform resource identifier, a compact string used to identify abstract or physical resources.

URL = Universal Resource Locator uniform resource locator, a string that locates the main access mechanism of a resource. A standard URL must include: protocol, host, port, path, parameter, anchor.

URN = Universal Resource Name uniform resource name that identifies the resource by a unique name or ID in a specific namespace.

Easy to understand and explain

First of all, let me give you an example. one day, the general manager of a company gave me a business card with his title, Zhang San, general manager of Beijing XXX Company, and his office address, general manager office of Beijing XXX Company, 35 Chang'an Street, Haidian District, Beijing. well, I bragged to my friends later. I know Zhang San, general manager of Beijing XXX Company. My friends all know that the general manager of Beijing XXX Company is a man named Zhang San, so this title corresponds to Zhang San. As soon as it comes to this title, everyone knows that he is talking about Zhang San. When it comes to the online world, the title is called URI. As long as you give me a URI, I will know what it represents. For example, http://www.sina.com.cn represents Sina. Admin@qq.com represents someone's QQ Mail, and your qq number is also a URI (your QQ account can be identified in Tencent server). URI is the title of network resources. Everything in the network world can be marked and distinguished by URI tags.

OK, now there is a problem. You now know that the general manager of Beijing XXX Company is Zhang San, and the "general manager of Beijing XXX Company" is Zhang San's URI. However, I will ask you to meet Zhang San in person. Can you do that? You certainly can't, because you don't know his address, although you have his URI title, but other than that, you don't know anything about him, so if you want to locate him, you must get his office address. Through the address "General Manager's Office of Beijing XXX Company, 35 Chang'an Street, Haidian District, Beijing", you will find Zhang San. Reflect to the network world, every resource in the network world not only has its own title, but also can be accessed and found, so the network address is necessary, otherwise, the existence of this network resource does not have any meaning, this address is called URL.

From the above description, we can find that URI emphasizes naming resources, and URL emphasizes locating resources, but you will find that URL obviously contains more information than URI. I can also know that Zhang San is the general manager through URL, and I also know his address, so in most cases, people find it too troublesome to name and give addresses to a network resource, so just use the address as an address. It is also used as a tag name, so URL also plays the role of URI in the WWW World wide Web, but it has more meaning than URI. I not only know your name, I also know where you are. What we type in the browser is URL, because the purpose of our input is to find a certain resource, and of course you are right to type URI, because URL is also URI.

Summary: URI marks a network resource, that's all; URL marks an WWW Internet resource (marked with an address) and gives his access address. (URI is Uniform Resource Identifier, which means a resource; URL is Uniform Resource Locator, which means an address, which is really difficult to understand just by looking at the abbreviations.)

URL is a subset of URI. All URL is URI, but not every URI is URL, and it may be URN.

Thank you for your reading, the above is the content of "how to understand the three elements of web front-end". After the study of this article, I believe you have a deeper understanding of how to understand the three elements of web front-end, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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