出于安全考虑，默认浏览器不能访问剪切板，需要开启才行，但是不是所有人都知道都会这么做，所以用了flash解决这个问题，flash可以访问

解决浏览器兼容性问题

只是一个font icon啊

不好意思，是我自己没看清楚，是有用到flash，@llffzzk 说的对，github用的是这个插件:zeroclipboard

This library is fully compatible with Flash Player 11.0.0 and above,
which requires that the clipboard copy operation be initiated by a
user click event inside the Flash movie. This is achieved by
automatically floating the invisible movie on top of a DOM element of
your choice. Standard mouse events are even propagated out to your DOM
element, so you can still have rollover and mousedown effects with
just a little extra effort.

Ubuntu上Chromium没装flash，果断没有复制按钮。。

主要是兼容性问题吧，虽然有些浏览器提供了复制的API，但是并不通用