I have example data like this

let datas = [
  { no : '1', list: [ {val: '1'}, {val: '3'},{val: '4'}] },
  { no : '2', list: [ {valNew: '11'}, {valNew: '13'},{valNew: '14'}] }
]

his expectations are like this

let datas = [
  { no : '1', list: [ {val: '1'}, { val: '2'}, { val: '3'},{val: '4'}] },
  { no : '2', list: [ {valNew: '11'}, {valNew: '13'},{valNew: '14'}] }
]

I've tried like this

const handleDuplicate = (index, idx, item) => {
let data = [...datas.listInvoice]
      data[index] = {
        ...data[index] = {
          ...data[index],
          invoices: [...data[index].invoices.slice(idx+1, 0, item)]
        }
      }
     
      setDatas(prevState => {
        return {
          ...prevState,
          listInvoice: data
        }
      })
}

I want to add an object to an array with a certain position, but it always fails and the array inside invoices becomes [], what is the solution for this case?