The difference between css and javascript: 1. CSS refers to cascading style sheets, which is a markup language that separates style information from web content, while JavaScript is a dynamic scripting language; 2. CSS is used to modify Web page style, and javascript is used to realize the function of interaction between web pages and people.
The operating environment of this article: windows7 system, css3&&javascript version 1.8.5, Dell G3 computer.
Client web pages usually include web content, HTML, javascript and CSS. Among them, javascript (js for short) is a browser client script language, which is used to realize the function of interaction between web pages and people; CSS, cascading style sheets, is used to modify the style of web pages, that is, to make web pages look better.
CSS (Cascading Style Sheet) Cascading Style Sheet
Presentation - design the presentation style of the web page, that is, "how to display relevant content"
CSS is the style A markup language that separates information from web content. We use CSS to define styles for each element; it is mainly used to beautify HTML pages.
The syntax is: selector {property: value} (selector {property: value}).
You can modify the display, position and other styles of each element in the HTML document by setting the corresponding style attributes; such as modifying the color, font, font size, width and height, position, background, etc.
JS (JavaScript) a dynamic scripting language
Behavior (behavior) - controlling the behavior (effect) of the web page, that is, "how the content should react to events"
Use JavaScript code can make the front desk interactive (click events), and is often used to add a variety of dynamic functions to web pages to provide users with a smoother and more beautiful browsing effect. Usually JavaScript scripts realize their functions by embedding them in HTML.
Commonly used functions of JavaScript:
Embed dynamic text in HTML pages
Respond to browser events
Read and write HTML elements
Validate data before it is submitted to the server
Detect visitor browsing Server information
Control cookies, including creation and modification, etc.
[Recommended learning: javascript advanced tutorial 】
HTML page loading and parsing process:
The user enters the URL (assuming it is an HTML page and it is the first time to visit), the browser sends a request to the server A request is made and the server returns an html file.
The browser started loading the html code and found that there was a tag in the
tag that referenced an external CSS file.The browser sends a request for the CSS file again, and the server returns the CSS file.
The browser continues to load the code of the
part of the html, and the CSS file has been obtained, and the page can be rendered.The browser finds an tag in the code that references an image and sends a request to the server. At this time, the browser will not wait until the image is downloaded, but will continue to render the subsequent code.
The server returns the image file. Since the image occupies a certain area and affects the arrangement of subsequent paragraphs, the browser needs to go back and re-render this part of the code.
The browser found a
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