JSFiddle - React, Tailwind, and code Playground

JavaScript

var groupBy = function(xs, key) {
  return xs.reduce(function(rv, x) {
  console.log(x)
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

console.log(groupBy(['one', 'two', 'three'], 'length'));