edgabaldi/group_by.js

## group_by.js
const groupBy = (xs, key) => {
  return xs.reduce( (rv, x) => {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

console.log(groupBy(['one', 'two', 'three'], 'length'));
// => {3: ["one", "two"], 5: ["three"]}
	const groupBy = (xs, key) => {
	return xs.reduce( (rv, x) => {
	(rv[x[key]] = rv[x[key]] \|\| []).push(x);
	return rv;
	}, {});
	};

	console.log(groupBy(['one', 'two', 'three'], 'length'));
	// => {3: ["one", "two"], 5: ["three"]}