Pseudo-classes ni nini na zipi ni za kawaida?

Question

Accepted Answer

**Pseudo-class** (koloni moja `:`) huchagua vipengele kulingana na **hali** yake au **nafasi** yake — kitu ambacho hakiwezi kuelezwa na class ya kawaida, kama vile "wakati unapelekewa kishale" au "mtoto wa kwanza."

## Pseudo-classes za hali (mwingiliano)

```css
a:hover    { color: blue; }      /* mouse is over it */
a:focus    { outline: 2px solid; } /* keyboard/tab focus — keep for accessibility! */
button:active   { transform: scale(0.98); } /* while being pressed */
button:disabled { opacity: 0.5; } /* disabled form controls */
input:checked   { } /* checked checkbox/radio */
input:focus-visible { } /* focus only when keyboard-navigating (not mouse) */
```

Mpangilio wa viungo ni muhimu (LVHA): `:link`, `:visited`, `:hover`, `:active`.

## Pseudo-classes za muundo (nafasi)

```css
li:first-child  { } /* first li among its siblings */
li:last-child   { } /* last one */
li:nth-child(2) { } /* the 2nd */
li:nth-child(odd)  { } /* 1st, 3rd, 5th... — zebra striping */
li:nth-child(3n)   { } /* every 3rd */
p:only-child    { } /* a p that's the sole child */
```

`:nth-child()` ina nguvu — `2n` (sawa), `2n+1` (zisizo sawa), `3n` (kila ya tatu), n.k.

## Pseudo-classes za fomu na za kisasa

```css
input:required  { }
input:invalid   { border-color: red; }
:is(h1, h2, h3) { }  /* matches any — shortens selector lists */
.card:has(img)  { }  /* the "parent selector": a card that CONTAINS an img */
:not(.active)   { }  /* everything except .active */
```

## Pseudo-class dhidi ya pseudo-element

Pseudo-classes hutumia koloni **moja** (`:hover`, *hali*); pseudo-elements hutumia **mbili** (`::before`, *sehemu inayozalishwa*). Usizichanganye.

## Kwa nini ni muhimu

Pseudo-classes hukuruhusu kuweka mtindo kwa mwingiliano (hover/focus — muhimu kwa UI inayoweza kutumika na inayofikika) na muundo (striping, wa kwanza/wa mwisho) bila markup ya ziada au JavaScript.

Za kisasa (`:has`, `:is`, `:focus-visible`) hutatua matatizo ambayo hapo awali yalihitaji JS au selectors zinazojirudia.