Reference: https://www.w3schools.com/jsref/met_document_getelementbyid.asp https://www.w3schools.com/jsref/prop_html_innerhtml.asp https://www.w3schools.com/jsref/dom_obj_text.asp https://www.w3schools.com/tags/tag_button.asp https://www.w3schools.com/js/js_numbers.asp