code: function blankshield(target) {
      if (typeof target.length === 'undefined') {
        addEventListener(target, 'click', clickListener);
      } else if (typeof target !== 'string' && !(target instanceof String)) {
        for (var i = 0; i < target.length; i++) {
          addEventListener(target[i], 'click', clickListener);
        }
      }
    }
docs: blankshield is the main function exported by the library. It accepts an
  anchor element or array of elements, adding an event listener to each to
  help mitigate a potential reverse tabnabbing attack. For performance, any
  supplied object with a length attribute is assumed to be an array.
  
  @param {HTMLAnchorElement|HTMLAnchorElement[]} target