Merge objects of array having same value of a key but keep different values of another key as inner array

I have an array which has keys eventId and selectedNumber. In the array same eventid can be present in multiple objects but selectedNumber value will be always different. My aim is to make a nested array in which each object will have unique eventId But selectedNumber will become an array having numbers from each of those objects having the same eventId. I tried using lodash _.groupBy() method but its just combines the objects into array and add it to the value with key as eventId. I don’t want that. Anyway to do it?

Input:--

[{
  "eventId" : "636939dde9341f2fbbc7256e",
  "selectedNumber" : "20"
},
{
  "eventId" : "636939dde9341f2fbbc7256e",
  "selectedNumber" : "30"
},
{
  "eventId" : "63693a55e9341f2fbbc725c0",
  "selectedNumber" : "50"
}]

Result:--


[{
  "eventId" : "636939dde9341f2fbbc7256e",
  "selectedNumber" : ["20", "30"]
},
{
  "eventId" : "63693a55e9341f2fbbc725c0",
  "selectedNumber" : "50"
}]