<div id="test" style="background: var(--bg-white);">Test</div>

<script>

 const target = document.querySelector('#test');
 
 // style is itarable
 console.log(target.style[Symbol.iterator]);
 
 // but doesn't include background in the iterator
 console.log(...target.style);
 
 // but background is iterable!
 console.log(Object.getOwnPropertyDescriptor(target.style, 'background'));
 
 // we can see it in Object.keys
 console.log(Object.keys(target.style).filter(name => name === 'background'));
 
 // so we can iterate it anyway
 for(const k in target.style){
    if(k === 'background'){
      console.log(target.style[k]);
    }
 }
 
   // Object.entries works too
 console.log(Object.entries(target.style).filter(([name]) => name === 'background'));
 
 // or access directly
 console.log(target.style.getPropertyValue('background'));
 console.log(target.style.background);
 
</script>