Refactoring JavaScript: Separation of Concerns - Markup Code on JS

html-on-js.js

//  ... variable declaration and setting of widgetID, widgetTitle, etc.
let widgetText = "JavaScript is Quirky";
let widgetHTML = '<div id=' + widgetId + '>' +
                       '<h2 id="' + widgetTitleId + '">' + widgetTitle + '</h2>' +
                        '<div id="' + widgetContentId + '" style="' + widgetContentStyles + '">' +
                            widgetText +
                        '</div>' +
                    '</div>';

document.getElementById("widget-container").innerHTML = widgetHTML;