code: function _isValid(el, currentPath) {
  	// Link has no destination URL
  	if (! el.href) { return false; }
  
  	// Link opens a new browser window
  	if (el.target === '_blank') { return false; }
  
  	// Link is not absolute URL
  	if (! /https?:/.test(el.href)) { return false; }
  
  	// Link is a download
  	if (el.hasAttribute('download')) { return false; }
  
  	// Link is supposed to be ignored
  	if (el.hasAttribute('data-static')) { return false; }
  
  	// Link is external URL
  	if (el.host && el.host !== location.host) { return false; }
  
  	// Link is current page, but with a hash added
  	if (el.hash && el.pathname === currentPath) { return false; }
  
  	return true;
  }
docs: Determine if path is valid for history navigation
  
  @param {HTMLElement} el
  @param {string} [currentPath]
  @returns {boolean}
  @private