mui中使用tap事件为何点击以后页面会刷新回到原来的状态啊??

var flag = 1;
var focusIcon = $('.focusIcon');
for (var i = 0; i < focusIcon.length; i++) {
focusIcon[i].addEventListener('tap', function(e) {
e.preventDefault();
if (flag) {
this.className = 'focus';
flag = 0;
} else {
this.className = 'focusIcon';
flag = 1;
}
});
}
实现关注的功能图标变化