code: function _getElements(input) {
        var elements;
        if (typeof input === 'string' || input instanceof String) {
          // See https://davidwalsh.name/nodelist-array for the technique transforming nodeList -> Array.
          elements = [].slice.call(document.querySelectorAll(input));
          // I checked the 'input instanceof NodeList' test in IE9 and modern browsers and it worked for me.
        } else if (Array.isArray(input) || input instanceof NodeList) {
          elements = [].slice.call(input);
        } else {
          throw new Error('The selector provided to AnchorJS was invalid.');
        }
        return elements;
      }
docs: Turns a selector, nodeList, or array of elements into an array of elements (so we can use array methods).
  It also throws errors on any other inputs. Used to handle inputs to .add and .remove.
  @param  {String|Array|Nodelist} input - A CSS selector string targeting elements with anchor links,
  OR a nodeList / array containing the DOM elements.
  @returns {Array} - An array containing the elements we want.