объект style как работает присваивание

var div = document.getElementById('moving-div'); 
var placeHolder = document.createElement('div'); 
placeHolder.classList.add('anumber1'); 
placeHolder.style.height = div.offsetHeight + 'px'; 
 
var computedStyle = getComputedStyle(div, null); 
 
placeHolder.style.marginTop = computedStyle.marginTop; 
placeHolder.style.marginBottom = computedStyle.marginBottom; 
 
placeHolder.style.backgroundColor = '#C2C49b'; 
 
document.body.insertBefore(placeHolder, div) 
 
 div.style.position = 'absolute'; 
    div.style.right = div.style.top = 0;

Before Before Before 
 
<div id="moving-div"> 
Text Text Text<br> 
Text Text Text<br> 
</div> 
 
After After After