js如何判断鼠标是否悬停在两个div之一上？

1.鼠标悬停在a上时打开b
2.鼠标离开a且不在b上时则关闭b

2这个条件语句该怎么写？就是if()这段，功能代码不需要

$("#tag-btn1").on('mouseover',function(){
    $('#second-tag-div1').addClass('second-tag-div-active');
    $('.sidebar').addClass('z-index100');
    $('#secondary-content1').addClass('display-block');
});

$("#second-tag-div1").on('mouseover',function(){
    $('#second-tag-div1').addClass('second-tag-div-active');
    $('.sidebar').addClass('z-index100');
    $('#secondary-content1').addClass('display-block');
    var btn1 = document.getElementById('tag-btn1');
    var btn1 = document.getElementById('tag-btn1'):before;
    btn1.style.backgroundColor = "#00c680";
    btn1.style.color = "#FFF";
});

$("#tag-btn1").on('mouseout',function(){
    $('#second-tag-div1').removeClass('second-tag-div-active');
    $('.sidebar').removeClass('z-index100');
    $('#secondary-content1').removeClass('display-block');
});

$("#second-tag-div1").on('mouseout',function(){
    $('#second-tag-div1').removeClass('second-tag-div-active');
    $('.sidebar').removeClass('z-index100');
    $('#secondary-content1').removeClass('display-block');
});