HTML learning summary

First of all, we have to ask, what is html? The official explanation is: Hypertext Markup Language. What does that mean? Simply put, it is a special language used to create web pages. So, what is a web page? We say that a web page is a page displayed under a browser window, which is essentially a document.

A web page mainly has 3 elements: text, pictures and hyperlinks. With these 3 elements, we can create the simplest web page. However, when we actually do it, we have to consider this question: How to control the format and layout of the page? At the beginning, we used so-called "format control tags" and "tables" to achieve this. However, we soon discovered that this approach had serious drawbacks. For example, if we want the font, color, size, etc. of certain cells to change, we must modify those cells one by one. However, this is not the main thing. When we use scripting languages, we will find that another layout method will be more beneficial. Because we can more easily find the part we want to modify.

Now, let us consider another layout method: div+css style sheet. First, let's give an example of the advantages of this approach. 1. It is highly reproducible and can be cited multiple times. 2. Achieve the separation of content and format. 3. Precise control and fast search speed. Next, let's consider how to use it. The simplest way is to write style directly in the div tag, and then follow the content. However, if this is the case, the advantages of this layout method will not be apparent. The best way is to write styles in the head or outside, and then reference them. Here we have to mention two selectors. One is the class selector and the other is the id selector. It is through these selectors placed in the style sheet that we precisely manipulate styles. We will not go into details and will only discuss their differences. Simply put, class is a class and can be referenced multiple times; id is an identity and can only be referenced once. In fact, we must combine specific examples to truly explain it clearly.

Finally, let’s consider what is called “JavaScript”, a scripting language. First, we have to ask, what is a scripting language? What is the use? Consider this scenario: You have written a website and successfully published it. The user entered the correct information into your text box and clicked submit, only to find that nothing happened. This is of course because you did not write the reaction or action. Scripting languages ​​exist precisely to achieve this kind of reaction or action. In other words, the existence of a scripting language is absolutely necessary. In fact, in addition to this usage, we have a more common usage. As we mentioned earlier, we can control the style of a certain label through id or class. Similarly, we can find the id or class through scripting language and interactively manipulate the style of a certain tag.

The above is the basic content of web page production, namely HTML (content), CSS (style), JS (script/action).