try
setTimeout(x=> {
d.innerHTML='My content';
d.classList.remove('hide');
d.classList.add('scale')
},100);
.mydiv {
margin-left: 40px;
float: left;
transition: all 1s ease-in-out;
}
.scale { transform: scale(2); }
.hide { display:none; }
<div id='d' class="mydiv"></div>