leftGather gathers excess arguments into it from the left.

left_gather_decorator_recipe.js

/**
 * Gathering arguments from the right is easy in ES6 with the spread operator
 */
const [first, ...butFirst] = ['why', 'hello', 'there', 'little', 'droid'];

first
  //=> 'why'
butFirst
  //=> ["hello","there","little","droid"]

/**
 * With leftGather, we have to supply the length of the array we wish to use as
 * the result.
 */
const leftGather = (outputArrayLength) => {
  return function (inputArray) {
    return [inputArray.slice(0, inputArray.length - outputArrayLength + 1)].concat(
      inputArray.slice(inputArray.length - outputArrayLength + 1)
    );
  };
};

const [butLast, last] = leftGather(2)(['why', 'hello', 'there', 'little', 'droid']);

butLast
  //=> ["why","hello","there","little"]
last
  //=> 'droid'