title: How to add static data columns in dataTable existing columns
body: <p>Have requirement like API gives few columns of data and I need to add some static data columns. Is there any way to add few columns dynamically passing below like <code>{ data: this.test1 },{ data: this.test2 }</code>. I tried to add two columns but unable to fetch the data, getting blank cells.</p>
  <pre><code>  constructor(private http: HttpClient) {}
     public test1 =123;
     public test2 =234;
  </code></pre>
  <p>Initialization:</p>
  <pre><code>this.dtOptions = {
    pagingType: &quot;full_numbers&quot;,
    pageLength: 10,
    scrollCollapse: true,
    processing: true,
    destroy: true,
    scrollY:'50vh',
    columns: [
      { title: '&lt;input type=&quot;checkbox&quot; /&gt;' },
      { data: &quot;index&quot; },
      { data: &quot;firstname&quot; },
      { data: &quot;lastname&quot; },
      { data: this.test1 },
      { data: this.test2 }
    ],
  </code></pre>
  <p><a href="https://stackblitz.com/edit/angular-datatables-gitter-3c2rum?file=app%2Fapp.component.ts" rel="nofollow noreferrer">Stackblitz</a></p>