I want to add a transition time to my pure javascript toggle class function 
I knew how to code it but i forgot and now need some advice 

```
<!DOCTYPE html>
<html>
<head>

<style type="text/css">
#div{
    width: 200px;
    height: 150px;
}
.class1 {
    color: #f00;
    background-color: #2fadac;
}

.class2 {
    color: #00f;
    background-color: #c33;
}
</style>
</head>
<body>
<div id="div" class="class1">click here</div>
<script>
function classToggle() {
    this.classList.toggle('class1');
    this.classList.toggle('class2');
    style.cssText ="-webkit-transition: all 0.5s ease-in-out;";
}
document.querySelector('#div').addEventListener('click', classToggle);
</script>
</body>
</html>

```

any help would be appreciated