.replace in not working in js

I have data as

var data = '<template type="amp-mustache">
      <div class="comment-item pull-left bottommargin10">
         <div> 
            <span class="comment-user-logo pull-left"></span>
              <div class="pull-left margin-left-7">
                 <span class="comment-name"></span>
                 <div class="comment-date"></div>
                 <div class="comment-msg"></div>
              </div>
         </div>
      </div>
    </template>';

When I try to replace it

var newData = data.replace('<template type="amp-mustache">','');

It throws the following error

data.replace is not a funtion

Can anyone please help me. Thanks.

via TSR