focus:当focusable元素获得焦点时,不支持冒泡;
focusin:和focus一样,只是此事件支持冒泡;
blur:当focusable元素失去焦点时,不支持冒泡;
focusout:和blur一样,只是此事件支持冒泡;
对于同时支持这4个事件的浏览器,事件执行顺序为focusin > focus > focusout > blur

focus:当focusable元素获得焦点时,不支持冒泡;
focusin:和focus一样,只是此事件支持冒泡;
blur:当focusable元素失去焦点时,不支持冒泡;
focusout:和blur一样,只是此事件支持冒泡;
对于同时支持这4个事件的浏览器,事件执行顺序为focusin > focus > focusout > blur