131 lines
3 KiB
Markdown
131 lines
3 KiB
Markdown
status: #doc
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Tags: #html #css
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links: [[html-css]]
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Date: 2023-08-01
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___
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# css selector
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CSS selectors are used to "find" (or select) the HTML elements you want to style.
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We can divide CSS selectors into five categories:
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- Simple selectors (select elements based on name, id, class)
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- [Combinator selectors](https://www.w3schools.com/css/css_combinators.asp) (select elements based on a specific relationship between them)
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- [Pseudo-class selectors](https://www.w3schools.com/css/css_pseudo_classes.asp) (select elements based on a certain state)
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- [Pseudo-elements selectors](https://www.w3schools.com/css/css_pseudo_elements.asp) (select and style a part of an element)
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- [Attribute selectors](https://www.w3schools.com/css/css_attribute_selectors.asp) (select elements based on an attribute or attribute value)
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This page will explain the most basic CSS selectors.
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---
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## The CSS element Selector
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The element selector selects HTML elements based on the element name.
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Here, all `<p>` elements on the page will be center-aligned, with a red text color:
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```css
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p { text-align: center;
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color: red;}
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```
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---
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## The CSS id Selector
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The id selector uses the id attribute of an HTML element to select a specific element.
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The id of an element is unique within a page, so the id selector is used to select one unique element!
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```css
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#para1 { text-align: center;
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color: red;}
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```
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**Note:** An id name cannot start with a number!
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---
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## The CSS class Selector
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The class selector selects HTML elements with a specific class attribute.
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To select elements with a specific class, write a period (.) character, followed by the class name.
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In this example all HTML elements with class="center" will be red and center-aligned:
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```css
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.center { text-align: center;
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color: red;}
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```
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You can also specify that only specific HTML elements should be affected by a class.
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```css
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p.center { text-align: center;
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color: red;}
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```
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HTML elements can also refer to more than one class.
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In this example the `<p>` element will be styled according to class="center" and to class="large":
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```css
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<p class="center large">This paragraph refers to two classes.</p>
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```
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**Note:** A class name cannot start with a number!
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---
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## The CSS Universal Selector
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The universal selector `(*)` selects all HTML elements on the page.
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The CSS rule below will affect every HTML element on the page:
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```css
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* { text-align: center;
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color: blue;}
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```
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---
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## The CSS Grouping Selector
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The grouping selector selects all the HTML elements with the same style definitions.
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the h1, h2, and p elements have the same style definitions:
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``` css
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h1 { text-align: center;
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color: red;}
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h2 { text-align: center;
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color: red;}
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p { text-align: center;
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color: red;}
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```
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we have grouped the selectors from the code above:
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```css
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h1, h2, p { text-align: center;
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color: red;}
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```
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---
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# References
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https://www.w3schools.com/css/css_selectors.asp
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