JS map inside map creating an object returns unwanted indexes

I have a concrete problem which I don’t know how to solve cleanly.
The variables are given, so with roomtypes, restriction, rules variables I have to generate a request.

const rateRequest = {rate: []}
const roomtypes = [100, 101]
const restriction = {
  roomtypes: {
    100: [201],
    101: [201,202]
  }
}
const rules = [
  {
    field: 'price',
    value: 50
  },
  {
    field: 'release',
    value: 3
  }
]
roomtypes.forEach((roomtype) => 
    rateRequest.rate.push(
        ...restriction.roomtypes[roomtype].map((rateplanId) => ({
            roomtypeId: roomtype,
            rateplanId: rateplanId,
            ...rules.map((rule) => ({
                [rule.field]: rule.value,
            }))
        }))     
    )
)

console.log(rateRequest)

Produces this output:

{
  rate: [
    {
      '0': { price: 50 },
      '1': { release: 3 },
      roomtypeId: 100,
      rateplanId: 201
    },
    {
      '0': { price: 50 },
      '1': { release: 3 },
      roomtypeId: 101,
      rateplanId: 201
    },
    {
      '0': { price: 50 },
      '1': { release: 3 },
      roomtypeId: 101,
      rateplanId: 202
    }
  ]
}

But I want this ouput:

{
  rate: [
    {
      price: 50,
      release: 3,
      roomtypeId: 100,
      rateplanId: 201
    },
    {
      price: 50,
      release: 3,
      roomtypeId: 101,
      rateplanId: 201
    },
    {
      price: 50,
      release: 3,
      roomtypeId: 101,
      rateplanId: 202
    }
  ]
}

How can I remove this indexes? Cannot be possible to achieve with map inside another map?

>Solution :

You should spread a plain object, not an array. You can use Object.fromEntries for this.

Not your question, but you can replace the outer forEach with a flatMap and so produce the rate array in a more functional programming way (without push). And for the inner object literal you can use some shorter syntax if you name your variables right:

const roomtypes = [100, 101];
const restriction = {roomtypes: {100: [201],101: [201,202]}};
const rules = [{field: 'price',value: 50},{field: 'release',value: 3}];

const rateRequest = {
    rate: roomtypes.flatMap((roomtypeId) => 
        restriction.roomtypes[roomtypeId].map((rateplanId) => ({
            roomtypeId,
            rateplanId,
            ...Object.fromEntries(rules.map(({field, value}) =>
                [field, value]
            ))
        }))     
    )
};

console.log(rateRequest);