basically, reflects the implied roles from ARIA in HTML

role-reflect.js

var sectioningSelector = 'article,aside,main,nav,section'

var map = {
  'A': (el) => {
    return el.hasAttribute('href') ? 'link' : undefined
  },
  'AREA': (el) => {
    return el.hasAttribute('href') ? 'link' : undefined
  },
  'ARTICLE': 'article',
  'ASIDE': 'complimentary',
  'BUTTON': 'button',
  'DATALIST': 'listbox',
  'DD': 'definition',
  'DETAILS': 'group',
  'DIALOG': 'dialog',
  'DL': 'list',
  'DT': 'listitem',
  'FIGURE': 'figure',
  'FOOTER': (el) => {
    return !el.closest(sectioningSelector) ? 'contentinfo' : undefined
  },
  'FORM': 'form',
  'H1': 'heading',
  'H2': 'heading',
  'H3': 'heading',
  'H4': 'heading',
  'H5': 'heading',
  'H6': 'heading',
  'HEADER': (el) => {
    return !el.closest(sectioningSelector) ? 'banner' : 'undefined'
  },
  'HR': 'seperator',
  'IMG': (el) => {
    return (el.getAtttribute("alt") !== '') ? 'img': 'undefined'
  },
  'INPUT': (el) => {
    let type = el.type
 
    if (type === 'checkbox') {
      return 'checkbox'
    }
    if (type === 'number') {
      return 'spinbutton'
    }
    if (type === 'range') {
      return 'slider'
    }
    if (type === 'reset' || type === 'submit' || type === 'image' || type === 'button') {
      return 'button'
    }
    if (el.hasAttribute('list')) {
      if (type === 'text' 
          || type === 'search' 
          || type === 'tel' 
          || type === 'url' 
          || type=== 'email'
      ) {
        return 'combobox'
      }
    } else {
      if (type === 'email' || type === 'url' || type === 'text' || type=== 'tel') {
        return 'textbox'
      }
      if (type === 'search') {
        return 'searchbox'
      }
    }
  },
  'LI': (el) => { 
    var tagName = el.parentElement.tagName;
    return (tagName === 'OL' || tagName === 'UL') ? 'listitem' : undefined
  },
  'LINK': (el) => { return el.hasAttribute('href') ? 'link' : undefined },
  'MAIN': 'main',
  'MATH': 'math',
  'MENU': (el) => { return el.getAttribute('type') === 'context' ? 'menu' : undefined },
  'MENUITEM': (el) => { 
    var type = el.getAttribute('type') 
    if (type === 'command') {
      return 'menuitem'
    }
    if (type === 'checkbox') {
      return 'menuitemcheckbox'
    } 
    if (type === 'radio') {
      return 'menuitemradio'
    }
  },
  'NAV': 'navigation',
  'OL': 'list',
  'OPTGROUP': 'group',
  'OPTION': (el) => {
    el.matches('select,optgroup,datalist>option') ? 'option' : undefined
  },
  'OUTPUT': 'status',
  'PROGRESS': 'progressbar',
  'SECTION': 'region',
  'SELECT': 'listbox',
  'SUMMARY': 'button',
  'TABLE': 'table',
  'TEXTAREA': 'textbox',
  'TBODY': 'rowgroup',
  'THEAD': 'rowgroup',
  'TFOOT': 'rowgroup',
  'TD': 'cell',
  'TH': 'rowheader',
  'TR': 'row',
  'UL': 'list'
}
var mo = new MutationObserver((mutations) => {
  mutations.forEach((record) => {
    record.addedNodes.forEach((node) => {
      if (node.nodeType === 1 && !node.hasAttribute('role')){
        var key = node.nodeName,
            val = map[key]
        if (val) {
          if (typeof val === 'function') {
            val = val(node)
          }
          node.setAttribute('role', val)
        }
      }
    })
  })
});
mo.observe(document.documentElement, { 
  childList: true,
  subtree: true
})