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

function groupBy(array, callback) {
  var object = {};

  for (var i = 0; i < array.length; i++) {
    var item = array[i];
    var key = callback(item);

    if (object.hasOwnProperty(key)) {
      object[key].push(item);
    } else {
      object[key] = [item];
    }
  }

  return object;
};

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

var byId = groupBy(list, function(i) {
  return i.id;
});

console.log(byId);

var byNameLength = groupBy(list, function(i) {
  return i.name.length;
});

console.log(byNameLength);