Question from a beginner: Unexpected JS behavior

Question

I'm having a hard time wrapping my head around this one.

I have an array of objects, each object has three key/value pairs:

1. index = which is simply the index number in the array.
2. order = a sequential value that should always begin at 1 (basically index + 1).
3. name = some text value which has no effect.

The original state of the array looks like this:

var arrayOfObjects = [
  {
    index:0,
    order:1,
    name:"Some name"
  },
  {
    index:1,
    order:2,
    name:"Some other name"
  }
];

I created a function to duplicate the first object in the array [0]

function duplicateObject (){
  arrayOfObjects.splice(0,0,arrayOfObjects[0]);
}

Now the array looks like this -which is correct:

var arrayOfObjects = [
  {
    index:0,
    order:1,
    name:"Some name"
  },
  {
    index:0,
    order:1,
    name:"Some name"
  },
  {
    index:1,
    order:2,
    name:"Some other name"
  }
];

I've created another function to reset/overwrite the index and order values all over, I'll call this function from within the previous function (duplicateObject):

function resetNumbers (){
  for (let i=0; i < arrayOfObjects.length; i++){
    arrayOfObjects[i].index = i;
    arrayOfObjects[i].order = i + 1;
  }
  console.log(arrayOfObjects);
}

To my understanding, I should be getting:

var arrayOfObjects = [
  {
    index:0,
    order:1,
    name:"Some name"
  },
  {
    index:1,
    order:2,
    name:"Some name"
  },
  {
    index:2,
    order:3,
    name:"Some other name"
  }
];

But what I'm actually getting:

var arrayOfObjects = [
  {
    index:0,
    order:2,
    name:"Some name"
  },
  {
    index:0,
    order:2,
    name:"Some name"
  },
  {
    index:1,
    order:3,
    name:"Some other name"
  }
];

I don't understand why the resetNumbers function is not doing it's job. Can someone please help me understand?

Here is the entire code:

var arrayOfObjects = [{
    index: 0,
    order: 1,
    name: "Some name"
  },
  {
    index: 1,
    order: 2,
    name: "Some other name"
  }
];

function resetNumbers() {
  for (let i = 0; i < arrayOfObjects.length; i++) {
    arrayOfObjects[i].index = i;
    arrayOfObjects[i].order = i + 1;
  }
  console.log(arrayOfObjects);
}

function duplicateObject() {
  arrayOfObjects.splice(0, 0, arrayOfObjects[0]);
  resetNumbers();
}

//start the code
duplicateObject();