Does id belong to html?

id belongs to html. ID is a global attribute in HTML, which can be used to configure the common behavior of all elements and can be used on any element. The id attribute is used to give a unique name (identifier) ​​to a tag. When using CSS or JavaScript to operate this tag, you can find the tag through the id attribute.

The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.

id is a global attribute in HTML, which can be used to configure the common behavior of all elements and can be used on any element.

Commonly used global attributes include: class, hidden, id, lang, style, title, dir, contenteditable, etc.

HTML id attribute

The id attribute is used to give a unique name (identifier) ​​to a tag. When we use CSS or JavaScript to operate this tag, we can find the tag through the id attribute.

Defining the id attribute for the tag can provide us with a lot of convenience, such as:

• If the tag has the id attribute as a unique identifier, it is very convenient to use the id attribute Locate the tag;

• If the HTML document contains multiple tags with the same name, you can easily distinguish them by using the uniqueness of the id attribute.

Note: The value of the id attribute must be unique in an HTML document.

Syntax:

<element id="id值">

Naming rules for id values:

• Must start with the letters A-Z or a-z

• The following characters: letters (A-Za-z), numbers (0-9), hyphens ("-"), underscores ("_"), colons (":") and the period (".")

• Values ​​are case-sensitive

The sample code is as follows:

<input type="text" id="username" />
<div id="content">PHP中文网</div>
<p id="url">https://www.php.cn/</p>

Use the id attribute in CSS--id selector

The id selector can specify a specific style for HTML elements marked with a specific id.

The HTML element uses the id attribute to set the id selector, and the id selector in CSS is defined with "#".

The syntax structure is as follows:

#ID {
  属性 : 属性值;
}

The usage is similar to the class selector, so I won’t go into details here. Just note that the id attribute is unique and cannot be repeated.

An ID value can only appear once in an HTML document, that is, an ID can only uniquely identify one element (not a type of element, but an element).

That is, the id of the element is unique in the page, so the id selector is used to select a unique element!

Example:

#div1{
    background:rgb(200,200,0);
    color:blue;
    font-size:20px;
}

Running results

<p>这是一个段落</p>
<p id="div1">这是一个段落</p>

##Note: Due to the uniqueness of the id attribute, CSS is generally used for styling Do not use this selector, and the main purpose of this selector is to do js special effects

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