JavaScript 事件对象的兼容性方案

HTML:

<div>123</div>

CSS:

div {
    width: 100px;
    height: 100px;
    background-color: pink;
}

JS:
传统注册方式:

var div = document.querySelector('div');
div.onclick = function(e) {
    e = e || window.event;
    console.log(e);
}

attachEvent事件监听方式:

div.addEventListener('click', function(e) {
    e = e || window.event;
    console.log(e);
})