css 선택자 종류
Simple selectors: select elements based on name, id, class
The CSS element Selector
선택자로 요소를 선택하는 방법이다.
Example
Here, all <p> elements on the page will be center-aligned, with a red text color:
p {
text-align: center;
color: red;
}
The CSS id Selector
The id selector uses the id attribute of an HTML element to select a specific element.
The id of an element is unique within a page, so the id selector is used to select one unique element!
To select an element with a specific id, write a hash (#) character, followed by the id of the element.
Example
The CSS rule below will be applied to the HTML element with id=”para1″:
#para1 {
text-align: center;
color: red;
}
The CSS class Selector
The class selector selects HTML elements with a specific class attribute.
To select elements with a specific class, write a period (.) character, followed by the class name.
example
In this example all HTML elements with class=”center” will be red and center-aligned:
.center {
text-align: center;
color: red;
}
You can also specify that only specific HTML elements should be affected by a class.
exapmle
In this example only <p> elements with class=”center” will be red and center-aligned:
p.center {
text-align: center;
color: red;
}
HTML elements can also refer to more than one class.
example
<p class="center large">This paragraph refers to two classes.</p>
The CSS Universal Selector
The universal selector (*) selects all HTML elements on the page.
example
The CSS rule below will affect every HTML element on the page:
* {
text-align: center;
color: blue;
}
The CSS Grouping Selector
The grouping selector selects all the HTML elements with the same style definitions.
Look at the following CSS code (the h1, h2, and p elements have the same style definitions):
h1 {
text-align: center;
color: red;
}
h2 {
text-align: center;
color: red;
}
p {
text-align: center;
color: red;
}
It will be better to group the selectors, to minimize the code.
To group selectors, separate each selector with a comma.
Example
In this example we have grouped the selectors from the code above:
h1, h2, p {
text-align: center;
color: red;
}
Combinator selectors: select elements based on a specific relationship between them
Descendant Selector
The descendant selector matches all elements that are descendants of a specified element.
The following example selects all <p> elements inside <div> elements:
Example
div p {
background-color: yellow;
}
Child Selector (>)
The child selector selects all elements that are the children of a specified element.
The following example selects all <p> elements that are children of a <div> element:
Example
div > p {
background-color: yellow;
}
Adjacent Sibling Selector (+)
The adjacent sibling selector is used to select an element that is directly after another specific element.
Sibling elements must have the same parent element, and “adjacent” means “immediately following”.
The following example selects the first <p> element that are placed immediately after <div> elements:
Example
div + p {
background-color: yellow;
}
General Sibling Selector (~)
The general sibling selector selects all elements that are next siblings of a specified element.
The following example selects all <p> elements that are next siblings of <div> elements:
Example
div ~ p {
background-color: yellow;
}
CSS Pseudo-classes
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 */
a:active {
color: #0000FF;
}
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;
}
Hover on <div>
An example of using the :hover pseudo-class on a <div> element:
Example
div:hover {
background-color: blue;
}
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;
}
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;
}
Match all <i> elements in all first child <p> elements
In the following example, the selector matches the first <i> element in all <p> elements:
Example
p:first-child i {
color: blue;
}
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
<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>
</body>
</html>
All CSS Pseudo Classes
| Selector | Example | Example 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 |
CSS Pseudo-elements
Syntax
The syntax of pseudo-elements:
selector::pseudo-element {
property: value;
}
The ::first-line Pseudo-element
The ::first-line pseudo-element is used to add a special style to the first line of a text.
The following example formats the first line of the text in all <p> elements:
Example
p::first-line {
color: #ff0000;
font-variant: small-caps;
}
Note: The ::first-line pseudo-element can only be applied to block-level elements.
The following properties apply to the ::first-line pseudo-element:
Notice the double colon notation – ::first-line versus :first-line
The double colon replaced the single-colon notation for pseudo-elements in CSS3. This was an attempt from W3C to distinguish between pseudo-classes and pseudo-elements.
The single-colon syntax was used for both pseudo-classes and pseudo-elements in CSS2 and CSS1.
For backward compatibility, the single-colon syntax is acceptable for CSS2 and CSS1 pseudo-elements.
The ::first-letter Pseudo-element
The ::first-letter pseudo-element is used to add a special style to the first letter of a text.
The following example formats the first letter of the text in all <p> elements:
Example
p::first-letter {
color: #ff0000;
font-size: xx-large;
}
Note: The ::first-letter pseudo-element can only be applied to block-level elements.
The following properties apply to the ::first-letter pseudo- element:
Pseudo-elements and HTML Classes
Pseudo-elements can be combined with HTML classes:
Example
p.intro::first-letter {
color: #ff0000;
font-size: 200%;
}
The example above will display the first letter of paragraphs with class=”intro”, in red and in a larger size.
Multiple Pseudo-elements
Several pseudo-elements can also be combined.
In the following example, the first letter of a paragraph will be red, in an xx-large font size. The rest of the first line will be blue, and in small-caps. The rest of the paragraph will be the default font size and color:
Example
p::first-letter {
color: #ff0000;
font-size: xx-large;
}
p::first-line {
color: #0000ff;
font-variant: small-caps;
}
CSS – The ::before Pseudo-element
The ::before pseudo-element can be used to insert some content before the content of an element.
The following example inserts an image before the content of each <h1> element:
Example
h1::before {
content: url(smiley.gif);
}
CSS – The ::after Pseudo-element
The ::after pseudo-element can be used to insert some content after the content of an element.
The following example inserts an image after the content of each <h1> element:
Example
h1::after {
content: url(smiley.gif);
}
CSS – The ::marker Pseudo-element
The ::marker pseudo-element selects the markers of list items.
The following example styles the markers of list items:
Example
::marker {
color: red;
font-size: 23px;
}
CSS – The ::selection Pseudo-element
The ::selection pseudo-element matches the portion of an element that is selected by a user.
The following CSS properties can be applied to ::selection: color, background, cursor, and outline.
The following example makes the selected text red on a yellow background:
Example
::selection {
color: red;
background: yellow;
}
All CSS Pseudo Elements
| Slector | Example | Example 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 |