_getAttributeToWatch() {
        let attributeToWatch;
        if (this.isInputElement) {
            attributeToWatch = 'value';
        } else {
            const nodeType = this.domElement.nodeType;
            if (nodeType === Node.ELEMENT_NODE ||
                nodeType === Node.DOCUMENT_NODE ||
                nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
                attributeToWatch = 'textContent';
            } else if (nodeType === Node.TEXT_NODE) {
                attributeToWatch = 'nodeValue';
            }
        }

        return attributeToWatch;
    }
Return the name of the object attribute that store the current formatted data in the DOM element.

@returns {string}
@private