in src/helper/dom.ts [225:234]
extendDomFunctionality = function (this: DomBuilder, domElement: HTMLElement): ExtendedHTMLElement {
const extendedElement: ExtendedHTMLElement = domElement as ExtendedHTMLElement;
extendedElement.addClass = this.addClass.bind(extendedElement);
extendedElement.removeClass = this.removeClass.bind(extendedElement);
extendedElement.toggleClass = this.toggleClass.bind(extendedElement);
extendedElement.hasClass = this.hasClass.bind(extendedElement);
extendedElement.insertChild = this.insertChild.bind(extendedElement);
extendedElement.clear = this.clearChildren.bind(extendedElement);
return extendedElement;
};