css

Overview

底下是一組CSS規則，由幾個部分所組成:

  • CSS Selector : 選擇要套用到哪些元素上 (p 的部分)
  • CSS 宣告 : color: red; 就是一條CSS 宣告，由以下組成:
    • 屬性
    • 值

每個宣告最後都要加上分號 ;

才不會造成錯誤!

將CSS加入網頁中

<head>
    <link rel="stylesheet" href="./style.css">

</head>

<head>
    <style>
        p {
            color: red;
        }
    </style>
</head>
  • <link rel="stylesheet">
  • <style>

或是

  • 直接寫在元素裡
<p style="color:red;">我是紅色的</p>

Debug

CSS Selector

CSS Selector

Simple Selector

透過元素名稱來選擇。

Class Selector

透過元素的Class來選擇。

ID Selector

透過元素的ID來選擇。

Simple (Element) Selector

p {
    color: red;
}

a {
    color: orange;
}

img {
    width: 200px;
}

Class Selector

/* <p class="text">、<span class="super text"> */
.text {
    border: 1px solid black;
}

.logo {
    width: 500px;
}

/* <p class="blue text">、<div class="super  blue text"> */
.blue.text {
    color: blue;
}

ID Selector

#menu {
    color: white;
}

#my-avatar {
    height: 200px;
    width: 200px;
}

#enemy {
    color: red;
    border: 1px solid black;
}

Universal Selector

/* Select every element */
* {
    color: red;
}

Multiple Selector with same rule

/* <div id="menu">、<div id="nav"> */
#menu, #nav {
    font-size: 16px;
}

Separate with comma ","

Specificity

  • inline style > ID > class > element selector
  • universal = 0
  • !important overrides every rules

 

  • if specificity is same, latter > former

More: link1、link2

!important

  • try to adjust the specificity before using !important
  • avoid using !important for it breaks default styles
  • NEVER use !important on site-wide rules
p {
    color: red !important;
}

CSS Units

Units

https://developer.mozilla.org/zh-CN/docs/Learn/CSS/Introduction_to_CSS/Values_and_units

  • absolute
    • px
    • cm、mm、in
  • relative
    • em
    • rem
    • vw、vh

CSS Colors

...

Color Name

More

RGB Color

rgb(RR, GG, BB)

RGB Color

rgba(RR, GG, BB, opacity)

Filter effect: rgba(0, 0, 0, 0.5)

HEX Color

#RRGGBB

Text style

Styles

  • color
  • font-size
  • font-family
  • text-transform
  • text-decoration

More: MDN

color

p {
    color: red;
}

div {
    color: blue;
}

font-size

p {
    font-size: 14px;
}

h1 {
    font-size: 1.85em;
}

font-family

p {
    font-family: Arial;
}

div {
    font-family: Consolas,微軟正黑體,"Arial",sans-serif;
}

serif v.s. sans-serif

monospace

font-style、font-weight

text-decoration

.italic {
    font-style: italic;
}

.bold {
    font-weight: bold;
}

.underline { /* or overline */
    text-decoration: underline;
}

.storke {
    text-decoration: line-through;
}

.decorated {
    text-decoration: line-through underline;
}

text-decoration

.underscore {
    text-decoration: underline red wavy;
}

  • text-decoration-line

  • text-decoration-style

  • text-decoration-color

text-align

.center.text {
    text-align: center;
}

.left.text {
    text-align: left;
}

.right.text {
    text-align: right;
}

More: Link

line-height, letter-spacing

.center.text {
    text-align: center;
}

.left.text {
    text-align: left;
}

.right.text {
    text-align: right;
}

More: Link

Border

Border

p {
    border: 2px solid red;
}

其他的樣式可以參考這邊 >

Ex:

border-radius

p {
    border: 2px solid red;
    border-radius: 10px;
}

Effect:

div {
    width: 200px;
    height: 200px;
    border: 2px solid red;
    border-radius: 50%;
}

Effect:

border-<direction>

div {
    border-top: 2px solid red;
    border-right: 2px solid green;
    border-bottom: 2px solid blue;
    border-left: 2px solid yellow;
}

border: none;

Disable the border.

div {
    border-top: 2px solid red;
    border-right: 2px solid red;
    border-left: 2px solid red;
}

div {
    border: 2px solid red;
    border-bottom: none;
}

Box Model

Box Model

Example

body, html {
    margin: 0;
    padding: 0;
}

height, weight

- height

  元素高度

- weight

  元素寬度

box-sizing

- content-box

  設定的 height 與 width 只會設定 content， padding 和

  border 會另外加上去，造成元素實際大小超過設定值。

- border-box

  設定長寬時會連 padding 與 border 一起考慮進去。

Background

background

  • background-color
  • background-image
  • background-position
  • background-size
  • background-repeat
  • background-attachment

background-color, image

div {
    background-color: yellow;
}

div {
    background-image: url("https://example.com/image.jpg");
}

background-position, size

background-repeat

div {
    background-image: url("https://example.com/image.jpg");
    background-position: center center;
    background-size: 100% 100%;
    background-repeat: no-repeat;
}

MDN

background-attachment

div {
    background-attachment: fixed;
}

div {
    background-attachment: scroll;
}

div {
    background-attachment: local;
}

More

Display

Displays

  • block

  • inline、inline-block

  • table

  • none

  • flex
  • grid

More: MDN

Displays

display: none

完全不渲染元素，也不會在文件中佔有位置。

visibility: hidden

與 display: none 類似，但實際上仍會占有空間。

CSS

By Tony Yang

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