css05 CSS Pseudo-classes

https://www.w3schools.com/css/css_pseudo_classes.asp

 

What are Pseudo-classes?

A pseudo-class is used to define a special state of an element.

For example, it can be used to:

  • Style an element when a user mouses over it
  • Style visited and unvisited links differently
  • Style an element when it gets focus

 pseudo

 

 

 

Syntax

The syntax of pseudo-classes:

selector:pseudo-class {
  property: value;
}

Anchor Pseudo-classes

Links can be displayed in different ways:

Example

/* unvisited link */
a:link {
  color: #FF0000;
}

/* visited link */
a:visited {
  color: #00FF00;
}

/* mouse over link */
a:hover {
  color: #FF00FF;
}

/* selected link  当在一个链接上点击时，它就会成为活动的（激活的） */
a:active {
  color: #0000FF;
}

Note:

a:hover MUST come after a:link and a:visited in the CSS definition in order to be effective!

a:active MUST come after a:hover in the CSS definition in order to be effective!

Pseudo-class names are not case-sensitive.

<!DOCTYPE html>
<html>

<head>
    <style>
        /* unvisited link */
        a:link {
            color: red;
        }

        /* visited link */
        a:visited {
            color: green;
        }

        /* mouse over link */
        a:hover {
            color: hotpink;
        }

        /* selected link */
        a:active {
            color: blue;
        }
    </style>
</head>

<body>

    <h2>Styling a link depending on state</h2>

    <p><b><a href="https://www.cnblogs.com/emanlee" target="_blank">This is a link</a></b></p>
    <p><b>Note:</b> a:hover MUST come after a:link and a:visited in the CSS definition in order to be effective.</p>
    <p><b>Note:</b> a:active MUST come after a:hover in the CSS definition in order to be effective.</p>

</body>

</html>

 

 

 

Pseudo-classes and HTML Classes

Pseudo-classes can be combined with HTML classes:

When you hover over the link in the example, it will change color:

Example

a.highlight:hover {
  color: #ff0000;
} 
<!DOCTYPE html>
<html>
<head>
    <style>
        a.highlight:hover {
            color: #ff0000;
            font-size: 22px;
        }
    </style>
</head>
<body>
    <h2>Pseudo-classes and HTML Classes</h2>

    <p>When you hover over the first link below, it will change color and font size:</p>

    <p><a class="highlight" href="css_syntax.asp">CSS Syntax</a></p>

    <p><a href="default.asp">CSS Tutorial</a></p>
</body>
</html>

 

Hover on <div>

An example of using the :hover pseudo-class on a <div> element:

Example

div:hover {
  background-color: blue;
} 
<!DOCTYPE html>
<html>
<head>
    <style>
        div {
            background-color: green;
            color: white;
            padding: 25px;
            text-align: center;
        }

        div:hover {
            background-color: blue;
        }
    </style>
</head>
<body>
    <p>Mouse over the div element below to change its background color:</p>
    <div>Mouse Over Me</div>
</body>
</html>

 

 

Simple Tooltip Hover

Hover over a <div> element to show a <p> element (like a tooltip):

Hover over me to show the <p> element.

Example

p {
  display: none;
  background-color: yellow;
  padding: 20px;
}

div:hover p {
  display: block;
} 
<!DOCTYPE html>
<html>
<head>
<style>
    p {
    display: none;
    background-color: yellow;
    padding: 20px;
    }

    div:hover p {
    display: block;
    }
</style>
</head>
<body>
    <div>Hover over this div element to show the p element
    <p>Tada! Here I am!</p>
    </div>
</body>
</html>

 

 


CSS - The :first-child Pseudo-class

The :first-child pseudo-class matches a specified element that is the first child of another element.

Match the first <p> element

In the following example, the selector matches any <p> element that is the first child of any element:

Example

p:first-child {
  color: blue;
} 
<!DOCTYPE html>
<html>
<head>
<style>
p:first-child {
  color: blue;
} 
</style>
</head>
<body>

    <p>This is some text.</p>
    <p>This is some text.</p>

    <div>
        <p>This is some text.</p>
        <p>This is some text.</p>
    </div>

</body>
</html>

 

 

Match the first <i> element in all <p> elements

In the following example, the selector matches the first <i> element in all <p> elements:

Example

p i:first-child {
  color: blue;
} 
<!DOCTYPE html>
<html>
<head>
<style>
p i:first-child {
  color: blue;
} 
</style>
</head>
<body>
    <p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>
    <p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>
</body>
</html>

 

 

Match all <i> elements in all first child <p> elements

In the following example, the selector matches all <i> elements in <p> elements that are the first child of another element:

Example

p:first-child i {
  color: blue;
} 
<!DOCTYPE html>
<html>
<head>
<style>
p:first-child i {
  color: blue;
} 
</style>
</head>
<body>

<p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>
<p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>

<div>
  <p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>
  <p>I am a <i>strong</i> person. I am a <i>strong</i> person.</p>
</div>

</body>
</html>

 

 

 

CSS - The :lang Pseudo-class

The :lang pseudo-class allows you to define special rules for different languages.

In the example below, :lang defines the quotation marks for <q> elements with lang="no":

Example


<!DOCTYPE html>
<html>
<head>
<style>
q:lang(no) {
  quotes: "~" "~";
}
</style>
</head>
<body>

<p>Some text <q lang="no">A quote in a paragraph</q> Some text.</p>
<p>In this example, :lang defines the quotation marks for q elements with lang="no":</p>

</body>
</html>

 

 


All CSS Pseudo Classes

SelectorExampleExample description
:active a:active Selects the active link
:checked input:checked Selects every checked <input> element
:disabled input:disabled Selects every disabled <input> element
:empty p:empty Selects every <p> element that has no children
:enabled input:enabled Selects every enabled <input> element
:first-child p:first-child Selects every <p> elements that is the first child of its parent
:first-of-type p:first-of-type Selects every <p> element that is the first <p> element of its parent
:focus input:focus Selects the <input> element that has focus
:hover a:hover Selects links on mouse over
:in-range input:in-range Selects <input> elements with a value within a specified range
:invalid input:invalid Selects all <input> elements with an invalid value
:lang(language) p:lang(it) Selects every <p> element with a lang attribute value starting with "it"
:last-child p:last-child Selects every <p> elements that is the last child of its parent
:last-of-type p:last-of-type Selects every <p> element that is the last <p> element of its parent
:link a:link Selects all unvisited links
:not(selector) :not(p) Selects every element that is not a <p> element
:nth-child(n) p:nth-child(2) Selects every <p> element that is the second child of its parent
:nth-last-child(n) p:nth-last-child(2) Selects every <p> element that is the second child of its parent, counting from the last child
:nth-last-of-type(n) p:nth-last-of-type(2) Selects every <p> element that is the second <p> element of its parent, counting from the last child
:nth-of-type(n) p:nth-of-type(2) Selects every <p> element that is the second <p> element of its parent
:only-of-type p:only-of-type Selects every <p> element that is the only <p> element of its parent
:only-child p:only-child Selects every <p> element that is the only child of its parent
:optional input:optional Selects <input> elements with no "required" attribute
:out-of-range input:out-of-range Selects <input> elements with a value outside a specified range
:read-only input:read-only Selects <input> elements with a "readonly" attribute specified
:read-write input:read-write Selects <input> elements with no "readonly" attribute
:required input:required Selects <input> elements with a "required" attribute specified
:root root Selects the document's root element
:target #news:target Selects the current active #news element (clicked on a URL containing that anchor name)
:valid input:valid Selects all <input> elements with a valid value
:visited a:visited Selects all visited links

All CSS Pseudo Elements

SelectorExampleExample description
::after p::after Insert content after every <p> element
::before p::before Insert content before every <p> element
::first-letter p::first-letter Selects the first letter of every <p> element
::first-line p::first-line Selects the first line of every <p> element
::marker ::marker Selects the markers of list items
::selection p::selection Selects the portion of an element that is selected by a user
posted @ 2024-05-28 20:46  emanlee  阅读(8)  评论(0)  编辑  收藏  举报