DOMParser

getData 1

async function getData() {
    let url = "your api url";
    let data = await (await fetch(url)).json();
    let productReviewTemplate = $('#template').html();
    let template = _.template(productReviewTemplate);
    $("#container").append(template({productReviews : data}));
}

getData 2

async function getData() {
    let url = "your api url";
    let data = await (await fetch(url)).json();

    let elem = document.createElement("div");
    let content = document.createTextNode(data.content);
    elem.appendChild(content);

    let container = document.querySelector("#container");
    if (container) {
        container.appendChild(elem);
    }
}

getData 3

async function getData() {
    let url = "your api url";
    let reviews = await (await fetch(url)).json();
    let reviewTemplateHtml = document.querySelector("#product-review-tpl");
    if (reviewTemplateHtml) {
        let template = _.template(reviewTemplateHtml.innerHTML);
        let productReviews = document.querySelector(".product-reviews .list");
        if (productReviews) {
            let elems = new DOMParser().parseFromString(template({reviews}), "text/html");
            if (elems) {
                for (let elem of elems.body.childNodes) {
                    productReviews.appendChild(elem);
                }
            }
        }
    }
}

template

<script type="text/template" id="template">
  <% _.each(productReviews, function(review){ %>
      <div>
          <%= review.content %>
      </div>
  <% }) %>
</script>