In Javascript, how can I condense an array of objects, to an array of objects with arrays? [duplicate]

I've been searching for an answer but I'm not quite sure if I'm explaining the question properly to find the right answer. So essentially I have an array of many objects with much of the data being identical, I would like to condense the objects down to handle the data better

So I currently have something like:

var inStock =[
{"colour":"blue","type":"xs","item" : "shirt"},
{"colour":"blue","type":"xs","item" : "socks"},
{"colour":"pink","type":"xs","item" : "shirt"},
{"colour":"pink","type":"xl","item" : "socks"},
{"colour":"pink","type":"xl","item" : "shoes"}
];

and I would like to write some JS to convert it to something like:

var inStock = [
  { 
    "colour":"blue",
    "type":{
       "xs",["shirt","socks"]
    }
  },
  {
    "colour":"pink",
    "type":{
       "xs":["shirt"],
       "xl":["socks","shoes"]
    }
  }
];

I am essentially trying to organise the data into some sort of hierarchal system to organise the data better. I'm not sure if there is even a way to do this - but I'm open to other organisational suggestions that can help with condensing down the data.