按钮可以使用a或者
button标签。wap上要触发按钮的active态，必须触发ontouchstart事件，可以在body上加上ontouchstart=""全局触发。
按钮常见的操作场景：确定、取消、警示，分别对应class：weui_btn_primary、weui_btn_default、weui_btn_warn，每种场景都有自己的置灰态weui_btn_disabled，除此外还有一种镂空按钮weui_btn_plain_xxx，客户端webview里的按钮尺寸有两类，默认宽度100%，小型按钮宽度自适应，两边边框与文本间距0.75em：
<a href="javascript:;" class="weui_btn weui_btn_primary">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_disabled weui_btn_primary">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_warn">确认</a>
<a href="javascript:;" class="weui_btn weui_btn_disabled weui_btn_warn">确认</a>
<a href="javascript:;" class="weui_btn weui_btn_default">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_disabled weui_btn_default">按钮</a>
<div class="button_sp_area">
<a href="javascript:;" class="weui_btn weui_btn_plain_default">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_plain_primary">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_mini weui_btn_primary">按钮</a>
<a href="javascript:;" class="weui_btn weui_btn_mini weui_btn_default">按钮</a>
</div>
