Write a function “groupBy(array, callback)”

Question

I have a JavaScript task where I have to implement a function \"groupBy\", which, when given an array of objects and a function, returns an object w

Answer 1

Solution with pure JS:

var list = [{
    id: "102",
    name: "Alice"
  },
  {
    id: "205",
    name: "Bob",
    title: "Dr."
  },
  {
    id: "592",
    name: "Clyde",
    age: 32
  }
];

function groupBy(array, callback) {
  return array.reduce(function(store, item) {
    var key = callback(item);
    var value = store[key] || [];
    store[key] = value.concat([item]);
    return store;
  }, {})
}

console.log('example 1: ', groupBy(list, function(i) { return i.id; }));
console.log('example 2: ', groupBy(list, function(i) { return i.name.length; }));