CSS [Detailed explanation] Custom possessiones (also known as CSS variables)

CSS [Detailed explanation] Consuetudines possessiones (also known as CSS variables)

2024-07-12

variabiles declara - -

Variabilis nominatio praecepta

Suscipe numerum nominationis
Subsidiis nominans per audacia et spatia
Sinica et alia CJK texts subsidia
Nomina quae speciales notas habent ut $, [,], ^, (,), %, etc., non praebentur. His specialibus characteribus utendis, necesse est ut effugium backslash.

variabilis

Esse aliquem valorem velexpressio

 --direction: to top;
 --gradientColor: deeppink, deepskyblue;
 --gradient: to top, deeppink, deepskyblue;
 --linear-gradient: linear-gradient(to top, deeppink, deepskyblue);
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variabilis scope

Elementa descendentes possunt CSS elementa ab antecessore non mutatis statutis possidere.More proprietatibuspretii.

body {
    --color: deepskyblue;
}
.box {
    background-color: var(--color);
}
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global variabiles

:root {
  --borderColor: #ccc;
}
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Notae variabilium

Valores variabiles inter se transiri possunt

body {
    --green: #4CAF50;   
    --successColor: var(--green);
}
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css variables non possunt valores assignari sibi

/* 这种写法是非法的 */
--primary-color: var(--primary-color, #2a80eb);
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css variables non possunt adhiberi ut valor @media media pluma

:root {
    --maxWidth: 640px;
}
/* 不合法，语法无效 */
@media (max-width: var(--maxWidth)) {}
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CSS variabiles ut valores contenti proprietas nullum effectum habent

/* 无效 */
.bar::before {
    content: var(--percent);
}
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Variabilis var ()

p {  
   background-color: var(--any-what, deepskyblue); 
}
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deepskyblue estDefault valoremUtere deepskyblue cum -any-quid irritum est

Cum var () munus parametri illicitum est

body {
    --color: 20px;
    background-color: deeppink;
    background-color: var(--color, deepskyblue);
}
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Postrema color corporis color est pellucidus, quia valor initialis colori est pellucidus

Quamdiu primus modulus valor functionis var() validus est, etsi valor parametri est pulmentum, tamen normaliter parsed erit. Si primus valor parametri illicitus est, functio var() valorem initialem vel hereditarium valorem proprietatis hodiernae CSS (si hereditas est) resolvit, hoc est, secundum normas keyword globalis unset redditur. (Nota regulas reddere similes esse nec aequivalere cum directo posito keyword.)

Spatia linea a var () function

html {
    font-size: 14px;
}
body {
    --size: 20;
    font-size: 16px;
    font-size: var(--size)px;
}
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Extremum corpus font-size est 14px

Principium: Hic font-size: var(-size)px aequivalet pro font-size: 20 px. Cum var (-size) px sit grammatice legale, font-size:16px rete erit, et fontis magnitudo 14px ab elemento parentis tandem adhibebitur.

In melius consilium est:

body {
    --size: 20;   
    font-size: calc(var(--size) * 1px);
}
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or *

body {
    --size: 20px;   
    font-size: var(--size);
}
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js obtinet valorem css global variabilis

let borderColor= getComputedStyle(document.documentElement).getPropertyValue("--borderColor");
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// 获取 --color CSS变量值
var cssVarColor = getComputedStyle(box).getPropertyValue('--color'); 
// 输出cssVarColor值，结果是deepskyblue 
console.log(cssVarColor);
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js mutare valorem variabilium globalis CSS

document.documentElement.style.setProperty("--borderColor","green");
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js valorem CSS loci variables

<div id="box">
    <img src="1.jpg" style="border: 10px solid var(--color);">
</div>
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box.style.setProperty('--color', 'deepskyblue');
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Exempla practica

Valorem CSS variabilis in pagina proponere ope CSS counter

/* 有效 */
.bar::before {
    counter-reset: progress var(--percent);
    content: counter(progress);
}
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progressus talea

https://blog.csdn.net/weixin_41192489/article/details/121007837

svg imagines in pluribus locis

:root {
    --icon-check: url("data:image/svg+xml,%3Csvg viewBox='0 0 32 32'%3E%3Cpath 
fill='green' d='M28.027 5.161l-17.017 17.017-7.007-7.007-3.003 3.003 10.010 10.010 
20.020-20.020z'%3E%3C/path%3E%3C/svg%3E");
}
.icon-check {
    background: var(--icon-check) no-repeat center / 16px;
    /* 尺寸限制 */
    display: inline-block;
    width: 20px; height: 20px;
}
.valid-pass::after {
    content: var(--icon-check);
    /* 尺寸限制 */
    display: inline-block;
    width: 20px; height: 20px;
}
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Vide effectus https://demo.cssworld.cn/new/8/1-3.php

Button click effectus

Vide effectus https://demo.cssworld.cn/new/8/1-1.php

button {
    /* 这里的空格很重要 */
    --open: ;
    color: #2a80eb;
    -webkit-text-fill-color: #fff;
    border-radius: 4px;
    padding: 9px 20px;
    border: 1px solid var(--open, rgba(0,0,0,.1));
    box-shadow: var(--open, inset 0 1px 2px rgba(0,0,0,.1));
    background: var(--open, linear-gradient(#0003, transparent)) currentColor;
    text-shadow: var(--open, -1px -1px #0003);
    transition: .15s;
}
button:active {
    /* 任意全局关键字都可以 */
    --open: inherit;
}
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Exsequendam principium

Est spatium ante -apertum:, id est, valorem attributum -apertum est spatium, quod syntactice validum esse potest.Sed spatia non sunt invalida pro proprietatibus CSS sicut umbracula et background.
Post puga pyga ut felis "activum pseudo-classis", CSS enuntiatio -aperta:hereditas erit currens. valorem reddendi.

Custom CSS function keyword()

https://blog.csdn.net/weixin_41192489/article/details/121021277

Simulate attr () munus

https://blog.csdn.net/weixin_41192489/article/details/121022170

Technology sharing