溢出-y | overflow-y

overflow-y

当一个块级元素的内容在垂直方向发生溢出时，CSS属性overflow-y决定应该截断溢出内容，或者显示滚动条，或者直接显示溢出内容。

/* Content is not clipped */
overflow-y: visible;

/* Content is clipped, with no scrollbars */
overflow-y: hidden;

/* Content is clipped, with scrollbars */
overflow-y: scroll;

/* Let the browser decide */
overflow-y: auto;

/* Global values */
overflow-y: inherit;
overflow-y: initial;
overflow-y: unset;

初始值	visible
适用元素	non-replaced block-level elements and non-replaced inline-block elements
是否是继承属性	no
适用媒体	visual
计算值	as specified
Animation type	discrete
正规顺序	the unique non-ambiguous order defined by the formal grammar

语法

值

visible内容不会被截断，且可以显示在内容盒之外。hidden内容会被截断，且不会显示滚动条。scroll桌面浏览器总是显示滚动条，无论内容是否发生溢出。这可以避免滚动条的显示与消失所导致的元素尺寸不确定的问题。而打印机可能会打印溢出的内容。auto取决于浏览器本身。当内容发生溢出时，桌面浏览器如Firefox会显示滚动条。

正式语法

visible | hidden | scroll | auto

示例

HTML

<ul>
  <li><code>overflow-y:hidden</code> — hides the text outside the box
  <div id="div1">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
    </div>
  </li>

  <li><code>overflow-y:scroll</code> — always add a scrollbar
  <div id="div2">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
    </div>
  </li>

  <li><code>overflow-y:visible</code> — displays the text outside the box if needed
  <div id="div3">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
    </div>
  </li>

  <li><code>overflow-y:auto</code> — on most browser, equivalent to <code>scroll</code>
  <div id="div4">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
    </div>
  </li>
</ul>

CSS

#div1,
#div2,
#div3,
#div4 {
  border: 1px solid black;
  width:  250px;
  height: 100px;
}

#div1 { overflow-y: hidden; margin-bottom: 12px;}
#div2 { overflow-y: scroll; margin-bottom: 12px;}
#div3 { overflow-y: visible; margin-bottom: 120px;}
#div4 { overflow-y: auto; margin-bottom: 120px;}

结果

规范

Specification	Status	Comment
CSS Overflow Module Level 3The definition of 'overflow-y' in that specification.	Working Draft
CSS Basic Box ModelThe definition of 'overflow-y' in that specification.	Working Draft	Initial definition

浏览器兼容性

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	1.0	(Yes)	1.5 (1.8)	5.0 *	9.5	3.0

Feature	Android	Chrome for Android	Edge	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	1.0	(Yes)	(Yes)	1.0 (1.5)	(Yes)	(Yes)	(Yes)