Floats in CSS最初設(shè)計用于實現(xiàn)文字環(huán)繞圖片的布局，類似于雜志排版。它們通過將元素從正常文檔流中移除，并盡可能向左或向右對齊，使其他內(nèi)容如文本或內(nèi)聯(lián)元素圍繞其排列。例如，設(shè)置img { float: left; }后，旁邊的文本會環(huán)繞在圖片周圍，但可能導(dǎo)致父容器高度塌陷。使用floats進(jìn)行布局時，主要問題包括父容器不包含浮動元素、背景顏色或邊框消失以及后續(xù)元素意外上移。解決這些問題的方法有：1. 在浮動元素后添加帶有clear: both樣式的空元素；2. 使用clearfix hack，在父容器上應(yīng)用.clearfix::after { content: ""; display: table; clear: both; }；3. 對父容器設(shè)置overflow: hidden或overflow: auto。對于現(xiàn)代布局，建議優(yōu)先使用Flexbox或Grid，但在處理遺留代碼或局部浮動時，上述清除方法依然有效且實用。

Floats in CSS were originally designed to allow text to wrap around images, like in magazine layouts. Over time, they became a go-to tool for creating multi-column layouts before the rise of Flexbox and Grid. Even though floats are less commonly used for layout today, they still appear in legacy code and can be handy in specific cases.

How Floats Work

When you apply float: left or float: right to an element, it gets taken out of the normal document flow and shifts to the left or right as far as possible within its container. Other content, like text or inline elements, will wrap around it.

For example:

img {
  float: left;
  margin: 10px;
}

With this, any text next to the image will wrap around it instead of stacking below. But this behavior can cause parent containers to collapse — meaning they don’t expand to contain the floated elements.

Common Issues with Floats

The main problem comes when using floats for layout. Since floated elements are removed from the normal flow, their parent container may end up with a height of zero. This leads to overlapping content or broken layouts.

Here’s what typically happens:

• A container holds several floated boxes.
• The container doesn’t stretch to include them.
• Background colors or borders on the container disappear.
• Elements that follow might shift up unexpectedly.

This is where clearing floats becomes important.

Methods to Clear Floats

There are a few common techniques to clear floats and restore normal document flow:

• Using clear: both on a separate element
  You can add an empty element (like a <div>) after the floated elements and apply clear: both to it. This forces the page to resume below all floated items.

  <div style="clear: both;"></div>

• Using the clearfix hack
  Instead of adding extra markup, many developers use a CSS class called "clearfix" on the parent container. It looks like this:

  .clearfix::after {
    content: "";
    display: table;
    clear: both;
  }

  Apply this class to any container that wraps floated elements, and it’ll automatically expand to contain them.

• Using overflow property
  Another quick trick is applying overflow: hidden or overflow: auto to the parent container. This makes the container expand to contain floated children.

  .container {
    overflow: hidden;
  }

  Just be cautious — if you have content spilling outside the container, this could hide it unintentionally.

  When to Use Which Method

  If you're working on a modern layout and just need to handle a few floats here and there, the clearfix method is clean and reusable. If you're dealing with older codebases or need quick fixes without modifying HTML structure, using overflow can save time.

  But keep in mind: floats aren't meant for full-page layouts anymore. For more predictable and flexible designs, consider switching to Flexbox or CSS Grid.

  基本上就這些。

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