How to adjust this script for background image lazy load?

I have this little script:

```

// random
function randomImage(){
var images =[';
$images = get_field('header-images');
if( $images ): foreach( $images as $image ):
$arr = $image['url'];
echo json_encode($arr).",";
endforeach;
endif;
echo '];
var size = images.length;
var x = Math.floor(size * Math.random());
console.log(x);
var element = document.getElementsByClassName("l-header-image");
console.log(element);
element[0].style["background-image"] = "url("+ images[x] + ")";
}
document.addEventListener("DOMContentLoaded", randomImage);
';
?>
```

What this script do is loading background-image from array for div class "l-header-image lozad" with each page reload. The array is ACF gallery field.

So I need adjust this script for lozad background-image option :)

Any ideas? :)