Loop through array while creating one div.row and appending three div.col-lg-4
Currently your code accesses live DOM unnecessarily, which is slow. For example, it creates a row, then searches it by id in the document instead of returning directly. It's better to construct elements without attaching them to actual document, and attach when everything's done.

However, since you're using innerHTML there's no need to create DOM elements manually, just construct an overall HTML string and insert it in the document. The entire code boils down to:

createDiv: function() {
  document.getElementById("displayQuoteHere").insertAdjacentHTML('beforeend',
    this.finalDellEqArray().map(function(item, index) {
      var before = index % 3 &gt; 0 ? '' : '&lt;div class="row row-border" id="' + index + '"&gt;';
      var after = index % 3 &lt; 2 ? '' : '&lt;/div&gt;';
      return before + '&lt;div class="col-lg-4 text-center"&gt;' + item + '&lt;/div&gt;' + after;
    }).join('')
  );
},