list-view-mixin.js

  /**
    @private
    @method _reuseChildren
  */
  _reuseChildren: function(){
    var contentLength, childViews, childViewsLength,
        startingIndex, endingIndex, childView, attrs,
        contentIndex, visibleEndingIndex, maxContentIndex,
        contentIndexEnd, scrollTop, viewsNeededForViewport;

    scrollTop              = this.scrollTop;
    contentLength          = get(this, 'content.length');
    maxContentIndex        = max(contentLength - 1, 0);
    childViews             = this.getReusableChildViews();
    childViewsLength       =  childViews.length;

    viewsNeededForViewport = this._numChildViewsForViewport();
    startingIndex          = this._startingIndex();
    visibleEndingIndex     = startingIndex + viewsNeededForViewport;

    endingIndex            = min(maxContentIndex, visibleEndingIndex);

    contentIndexEnd        = min(visibleEndingIndex, startingIndex + childViewsLength);

    for (contentIndex = startingIndex; contentIndex < contentIndexEnd; contentIndex++) {
      if(childViewsLength !== viewsNeededForViewport){
        this._syncChildViews()
      }
      childView = childViews[contentIndex % viewsNeededForViewport];
      this._reuseChildForContentIndex(childView, contentIndex);
    }
  },