Introduction to the differences between name, id and class in html

In a page, there are many controls (elements or labels). In order to operate these tags more conveniently, it is necessary to mark these tags with an identity tag.

Directory

1. name: Specify the name of the label.

2. id: Specify the unique identifier of the tag.

3. class: Specify the class name of the label.

1. name

Specify the name of the label.

1.1 Format

<input type="text" name="username" />

1.2 Application Scenario

①form form: name can be used as the variable name transferred to the server form list; such as The name passed to the server above is: username='text value'.

②input type='radio'radio label: When the names of several radio label names are set to the same value, a radio selection operation will be performed.

<input type="radio" name=&#39;sex&#39;/>男<input type="radio" name=&#39;sex&#39;/>女

③Quickly obtain a group of tags with the same name: Get tags with the same name and perform operations together, such as: changing attributes and registering events wait.

function changtxtcolor() {    var txts = document.getElementsByName('txtcolor'); //获取所有name=txtcolor 的标签
    for (var i = 0; i < txts.length; i++) { //循环遍历标签，并把背景色改为red
        txts[i].style.backgroundColor = &#39;red&#39;;
    }
}

1.3 Features The value of the

name attribute is not unique in the current page.

2. id

specifies the unique identifier of the tag.

2.1 Format

<input type=password 
id
="userpwd" />

##2.2 Application scenario

①According to the unique ID number, quickly obtain the label object. For example: document.getElementById(id)

② Used as the value of the label label for attribute: Example: d305c5282d143dd49e6374acc3c8c7aa User name:

2.3 Features

The value of the id attribute must be unique in the current page.

3. class

Specifies the class name of the label.

3.1 Format

<input type=button 
class
="btnsubmit" />

3.2 Application Scenario

①CSS operation, put some specific styles into a class. If you need tags of this style, you can add this class.

3.3 Features

You can put multiple classes in one class attribute, but they must be separated by spaces; such as:

class
=
'btnsubmit btnopen'

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