Convert an array of similar objects into an object with a common property as key

PimpMyJsConsole-toHash.js

Array.prototype.toHash = function(key){
  let hashMap = {}
  this.forEach( (el) => {
    hashMap[el[key]] = el
  })
  return hashMap
}

/*
> var arr = [{id: "a", thing: 123}, {id: "b", thing2: 456}]
> arr.toHash("id")
< Object {a: Object, b: Object}
*/