::before (:before)

CSS에서, ::before는 선택한 요소의 첫 자식으로 의사 요소를 하나 생성합니다. 보통 content 속성과 함께 짝지어, 요소에 장식용 콘텐츠를 추가할 때 사용합니다. 기본값은 인라인입니다.

/* 링크 앞에 하트 추가 */
a::after {
  content: "♥";
}

참고: ::before::after로 생성한 의사 요소는 원본 요소의 서식 박스에 포함되므로, <img><br>대체 요소에 적용할 수 없습니다.

구문

/* CSS3 syntax */
::before

/* CSS2 syntax */
:before

참고: 의사 클래스의사 요소를 구분하기 위해 CSS3부터::before 구문을 도입했습니다. 그러나 브라우저는 CSS2 구문인 :before도 허용합니다.

예제

인용 표시 추가

One simple example of using ::before pseudo-elements is to provide quotation marks. Here we use both ::before and ::after to insert quotation characters.

HTML

<q>Some quotes,</q> he said, <q>are better than none.</q>

CSS

q::before {
  content: "«";
  color: blue;
}

q::after {
  content: "»";
  color: red;
}

Result

장식 예제

We can style text or images in the content property almost any way we want.

HTML

<span class="ribbon">Notice where the orange box is.</span>

CSS

.ribbon {
  background-color: #5BC8F7;
}

.ribbon::before {
  content: "Look at this orange box.";
  background-color: #FFBA10;
  border-color: black;
  border-style: dotted;
}

Result

할 일 목록

In this example we will create a simple to-do list using pseudo-elements. This method can often be used to add small touches to the UI and improve user experience.

HTML

<ul>
  <li>Buy milk</li>
  <li>Take the dog for a walk</li>
  <li>Exercise</li>
  <li>Write code</li>
  <li>Play music</li>
  <li>Relax</li>
</ul>

CSS

li {
  list-style-type: none;
  position: relative;
  margin: 2px;
  padding: 0.5em 0.5em 0.5em 2em;
  background: lightgrey;
  font-family: sans-serif;
}

li.done {
  background: #CCFF99;
}

li.done::before {
  content: '';
  position: absolute;
  border-color: #009933;
  border-style: solid;
  border-width: 0 0.3em 0.25em 0;
  height: 1em;
  top: 1.3em;
  left: 0.6em;
  margin-top: -1em;
  transform: rotate(45deg);
  width: 0.5em;
}

JavaScript

var list = document.querySelector('ul');
list.addEventListener('click', function(ev) {
  if (ev.target.tagName === 'LI') {
     ev.target.classList.toggle('done');
  }
}, false);

Here is the above code example running live. Note that there are no icons used, and the check-mark is actually the ::before that has been styled in CSS. Go ahead and get some stuff done.

Result

특수문자

As this is CSS; not HTML, you can not use markup entities in content values. If you need to use a special character, and can not enter it literally into your CSS content string, use a unicodeescape sequence, consistingof a backslash followed by the hexadecimal unicode value.

HTML

<ol>
  <li>Crack Eggs into bowl</li>
  <li>Add Milk</li>
  <li>Add Flour</li>
  <li aria-current='step'>Mix thoroughly into a smooth batter</li>
  <li>Pour a ladleful of batter onto a hot, greased, flat frying pan</li>
  <li>Fry until the top of the pancake loses its gloss</li>
  <li>Flip it over and fry for a couple more minutes</li>
  <li>serve with your favorite topping</li>
</ol>

CSS


li {
  padding:0.5em;
}

li[aria-current='step'] {
  font-weight:bold;
}

li[aria-current='step']::after {
  content: " \21E6"; /* Hexadecimal for Unicode Leftwards white arrow*/
  display: inline;
}

Result

명세

Specification Status Comment
CSS Pseudo-Elements Level 4
The definition of '::before' in that specification.
Working Draft No significant changes to the previous specification.
CSS Transitions Working Draft Allows transitions on properties defined on pseudo-elements.
CSS Animations Working Draft Allows animations on properties defined on pseudo-elements.
Selectors Level 3
The definition of '::before' in that specification.
Recommendation Introduces the two-colon syntax.
CSS Level 2 (Revision 1)
The definition of '::before' in that specification.
Recommendation Initial definition, using the one-colon syntax

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