code: function rememberRejections(filterFn) {
    const rejections = [];
  
    return {
      filter: function(item) {
        const allowed = filterFn(item);
  
        if (!allowed) {
          rejections.push(item);
        }
  
        return allowed;
      },
      rejections: rejections
    };
  }
docs: Wraps around a filter function and records all items that are excluded by it. Does not modify the function passed in.
  
  @param filterFn The fn to wrap around
  @returns {{filter: filter, rejections: Array}} The resulting filter function that remembers rejections, and an array
  array of the rejected items. As the filter function is used, the rejections array with be populated.