CSS過渡通過平滑動(dòng)畫實(shí)現(xiàn)CSS屬性值之間的切換，適用於按鈕懸停效果、菜單展開折疊等用戶交互場(chǎng)景。常見用法包括按鈕懸刻效果、下拉菜單漸顯、背景色漸變、圖片透明度或縮放變化。基本語法為transition: 屬性持續(xù)時(shí)間時(shí)序函數(shù)，可指定單個(gè)或多個(gè)屬性，也可使用all代表所有屬性，但需謹(jǐn)慎使用。時(shí)序函數(shù)如ease、linear、ease-in-out控制動(dòng)畫速度曲線，也可用cubic-bezier自定義。建議優(yōu)先使用opacity和transform以獲得更好性能，並結(jié)合@media (prefers-reduced-motion)提升可訪問性，JavaScript操作時(shí)注意避免跳幀。

CSS transitions let you smoothly animate changes between CSS property values, instead of having them switch instantly. They're commonly used for things like hover effects, button states, or UI feedback — basically anywhere you want a visual change to feel more natural and polished.

When to Use Transitions

Transitions work best when you're changing properties on user interaction (like :hover , :focus , or JavaScript-triggered class changes). For example, making a button slightly grow when hovered over, or fading in a dropdown menu.

They're not meant for complex animations — that's where keyframe animations come in. But for simple state changes, transitions are lightweight and easy to set up.

Here are some common use cases:

• Button hover effects
• Expanding/collapsing menus
• Changing background colors gradually
• Image opacity or scale on interaction

Basic Syntax

To create a transition, you usually define two things: which property to animate and how long the animation should take. The most basic syntax looks like this:

 transition-property: width;
transition-duration: 0.3s;

Or you can shorthand it:

 transition: width 0.3s ease;

You can also specify multiple properties by separating them with commas:

 transition: width 0.3s ease, background-color 0.5s linear;

And if you want all properties to transition, just write:

 transition: all 0.3s ease;

Just be careful with all — it can sometimes cause unintended animations on properties you didn't expect.

Controlling Transition Timing

Timing matters a lot in how smooth and natural your transitions feel. You can adjust both duration and timing function.

Duration is straightforward — it's how long the transition takes. Too short (like 0.1s) feels jarring; too long (like 2s) might frustrate users.

Timing functions control the speed curve of the transition. Common ones include:

• ease – starts slow, speeds up, then slows again (default)
• linear – constant speed from start to finish
• ease-in – starts slow, ends fast
• ease-out – starts fast, ends slow
• ease-in-out – symmetric acceleration/deceleration

For fine-tuning, you can use cubic-bezier curves to create custom timing curves. Tools like cubic-bezier.com help visualize them.

Tips for Smooth Transitions

Not all CSS properties animate well — stick to things like opacity , transform , and background-color for best performance. Avoid animating layout properties like width or height unless necessary, since they can trigger reflows.

Also, consider accessibility. Some users may prefer reduced motion, so you can add this to respect their preferences:

 @media (prefers-reduced-motion: no-preference) {
  /* your transitions here */
}

Another small but useful trick: if you're toggling classes via JavaScript, make sure the browser has time to register the initial state before triggering the transition. Sometimes a tiny delay ( requestAnimationFrame ) helps avoid skipped frames.

基本上就這些。

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