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How it works
Before getting started with Bootstrap’s modal component, be sure to read the following as our menu options have recently changed.
- Modals are built with HTML, CSS, and JavaScript. They’re positioned over everything else in the document and remove scroll from the
<body>so that modal content scrolls instead. - Clicking on the modal “backdrop” will automatically close the modal.
- Bootstrap only supports one modal window at a time. Nested modals aren’t supported as we believe them to be poor user experiences.
- Modals use
position: fixed, which can sometimes be a bit particular about its rendering. Whenever possible, place your modal HTML in a top-level position to avoid potential interference from other elements. You’ll likely run into issues when nesting a.modalwithin another fixed element. - Once again, due to
position: fixed, there are some caveats with using modals on mobile devices. See our browser support docs for details. - Due to how HTML5 defines its semantics, the
autofocusHTML attribute has no effect in Bootstrap modals. To achieve the same effect, use some custom JavaScript:
const myModal = document.getElementById('myModal')
const myInput = document.getElementById('myInput')
myModal.addEventListener('shown.bs.modal', () => {
myInput.focus()
})
The animation effect of this component is dependent on the prefers-reduced-motion media query. See the reduced motion section of our accessibility documentation.
Keep reading for demos and usage guidelines.
]]>当页面中a标签不需要任何跳转时，从原理上来讲，可分如下两种方法：当页面中a标签不需要任何跳转时，从原理上来讲，可分如下两种方法：当页面中a标签不需要任何跳转时，从原理上来讲，可分如下两种方法：当页面中a标签不需要任何跳转时，从原理上来讲，可分如下两种方法：
- 标签属性href，使其指向空或不返回任何内容。如：<a href=”javascript:void(0);” >点此无反应javascript:void(0)</a><a href=”javascript:;” >点此无反应javascript:</a>
- 标签事件onclick，阻止其默认行为。如：<a href=”” οnclick=”return false;”>return false;</a><a href=”#” οnclick=”return false;”>return false;</a>
注意：只有一个href=”#”是不可以的。
原理：
- 标签属性href=”javascript:void(0);” 关键是理解void(0)的含义。
javascript中void是一个操作符，该操作符指定要计算一个表达式但是不返回值
用法格式如下：
a). javascript:void (expression)
b). javascript:void expression
你以使用 void 操作符指定超级链接。表达式会被计算但是不会当前文档处装入任何内容。所以，javascript:void(0) 仅仅表示一个死链接。
只有href=”#”是不可以的，因为#包含了一个位置信息，默认的锚是#top 也就是网页的上端。我理解的锚是指网页中具体位置。
例如：
首先我们在网页body内最上面添加一个<span id=”top” name=”top”></span>
我们再到body内，需要出现点击后转到顶部位置添加，<a href=”#top”>回到顶部</a>
点击回到顶部即可让滚动回到顶部。
- 标签事件οnclick=”return false;” 在HTML代码中，无论你在哪里放置了onclick事件，并且返回值为false时，那么该处的默认行为将不会执行。这里的默认行为是指没有Onclick事件时原本的行为。
最后，我们来回顾下a标签的三种用法：
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