JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
	<div class="leftside">
        <div class="object"><span>object 1</span></div>
        <div class="object"><span>object 2</span></div>
        <div class="object"><span>object 3</span></div>
        <div class="object"><span>object 4</span></div>
	</div>
    <div class="rightside">
        
    </div>
</div>

CSS

.main {
    border: 4px solid #000;
    margin: 0 auto;
    position: relative;
    width:1182px;
    min-height: 200px;
}
    .leftside {
        border-right: 2px solid #ccc;
        float: left;
        height: 200px;
        width: 100px;float: left;
    }
        .object {
          background: #d3d3d3;
          border-bottom: 1px solid #ccc;
          height: 50px;
        }
            .object > span {
                line-height: 3em;
                padding: 0 20px;
            }
    
    .rightside {
        float: left;

        overflow: hidden;width: 100px;
  overflow: auto;
    }
        
        .row {
            float: left;
            width: 100%;
        }
            .row .item {
                float: left;
                height: 50px;
                width: 48px;
                border-left: 1px solid #ccc;
                border-bottom: 1px solid #ccc;
            }
                .row .item:first-child {border-left:none;}
                .row .item:last-child {
                    border-right: 1px solid #ccc;
                }

JavaScript

$('.object').each(function(){
    element = $('<div class="item"></div>');
    row = $("<div class='row'></div>");
    for(i=0;i<20;i++){
        row.append(element.clone());
    }
    $('.rightside').append(row)
});