Get closest parent element matching selector

getClosest.js

/**
 * Get closest DOM element up the tree that contains a class, ID, or data attribute
 * @param  {Node} elem       The base element
 * @param  {String} selector The class, id, data attribute, or tag to look for
 * @return {Node}            Element or Null if no match
 */
export function getClosest (elem, selector) {
  let firstChar = selector.charAt(0);

  // Get closest match
  for (; elem && elem !== document; elem = elem.parentNode ) {

    // If selector is a class
    if ( firstChar === '.' ) {
      if ( elem.classList.contains( selector.substr(1) ) ) {
        return elem;
      }
    }

    // If selector is an ID
    if ( firstChar === '#' ) {
      if ( elem.id === selector.substr(1) ) {
        return elem;
      }
    }

    // If selector is a data attribute
    if ( firstChar === '[' ) {
      if ( elem.hasAttribute( selector.substr(1, selector.length - 2) ) ) {
        return elem;
      }
    }

    // If selector is a tag
    if ( elem.tagName.toLowerCase() === selector ) {
      return elem;
    }
  }

  return false;
}