获取相同类名角度4的div的offsetWidth

Question

我想获得具有相同类名的div的offsetWidth：-“ offer-ads-wrap”。我正在获取HTMLCollection列表，长度为零。如何获得offsetwidth？我的html代码是：-

<div class="offer-ads-area"  *ngFor="let singleRest of restaurantListByTag">
    <div class="wraper">
        <div id="offer-ads-wrap" class="offer-ads-wrap add_sec">
            <h3>{{singleRest.name}}</h3>
            <ng-template #prev >
                <i
                 class="fa fa-arrow-circle-left fa-4x pointer"  aria-hidden="true">
                </i>
            </ng-template>
            <div (window:resize)="onNewResize($event)"
              ng2-carouselamos
              class="slides-wrapper"
              [width]="newDynamicWidth"
              [items]="singleRest.tag_map"
              [$item]="item"
              [$prev]="prev"
              [$next]="next">
            </div>
            <ng-template let-item let-i="index" #item>
                <div class="items"> 
                    <a href="#">
                        <figure><img src="../../assets/images/ad3.jpg"></figure>
                        <span class="menu-info">
                            <h5>{{ item.res_name }}</h5>
                            <span>{{ item.res_title_tag }}</span>
                        </span>
                    </a>
                </div>
            </ng-template>
            <ng-template #next >
                <i 
                class="fa fa-arrow-circle-right fa-4x pointer" aria-hidden="true"></i>
            </ng-template>                    
        </div>  
    </div>        
</div>

在我的TS文件中，我正在编写以下代码：-

let newDynamicWidthEl = document.getElementsByClassName("offer-ads-wrap");
      console.log(newDynamicWidthEl);

在控制台中，我的输出是：-

  

HTMLCollection [0]       0：div＃offer-ads-wrap.offer-ads-wrap.add_sec       1：div＃offer-ads-wrap.offer-ads-wrap.add_sec       2：div＃offer-ads-wrap.offer-ads-wrap.add_sec       3：div＃offer-ads-wrap.offer-ads-wrap.add_sec       长度：4       原始：HTMLCollection