Get index of Object inside Array and use it in a function

Question

In Javascript, is it possible to get the Index of the object (in an array of objects) and use it inside of the same object in a function?

For example:

const foo = [
  {
    id: 1,
    comments: getComments(this.index) // index of the object goes here
  },
  {
    id: 34,
    comments: getComments(this.index) // index of the object goes here
  },
  {
    id: 21,
    comments: getComments(this.index) // index of the object goes here
  }
]

const getComments = function(index) {
  return foo[index].id // return the ID of the actual object
}

Or is there a workaround for what I'm trying to achieve here?

Answer 1

Do it in two steps. First create the array of objects, then fill in the comments property by calling the function on each element.

 const foo = [ { id: 1, }, { id: 34, }, { id: 21, } ] foo.forEach(el => el.comments = getComments(el)); function getComments(obj) { return obj.id; } console.log(foo);

Answer 2

I assume this is for learning purposes as probably the use you are thinking could be implemented in a better way. The closest that you can do is this:

 let foo = [ { id: 1, }, { id: 34, }, { id: 21, } ] foo = foo.map( (elem, index) => ({...elem, comments: getComments(index)}) ) function getComments(index) { return foo[index].id // return the ID of the actual object } console.log(foo[2].comments)