How to Extract Json data from objects in typescript

I want to extract converted json from coverted excel data file but not working,
I want it to be in this form :

[{assignee: "", description: "seriene", duration: "24", floor: "Deluxe", id: 2, image_one: null,…},…]
0
: 
{assignee: "", description: "seriene", duration: "24", floor: "Deluxe", id: 2, image_one: null,…}
1
: 
{assignee: null, description: "seriene", duration: "24", floor: "Deluxe", id: 3, image_one: null,…}
2
: 
{assignee: null, description: "seriene", duration: "24", floor: "Deluxe", id: 5, image_one: null,…}

But shows this:

{Sheet1: [,…]}
Sheet1
: 
[,…]
0
: 
{First Name: "Samuel", Last Name: "Gyimah", Staff No.: "San50", Phone: 0, Address: "6th avenue tanoso",…}
Account
: 
111222554
Address
: 
"6th avenue tanoso"
Appointment
: 
45364.99990740741
Bank
: 
"UBA"
Branch
: 
"AAMUSTED"
Email
: 
"[email protected]"
First Name
: 
"Samuel"
ID No.
: 
"GHA7145562"
Joined
: 
45365.99990740741
Last Name
: 
"Gyimah"
Phone
: 
0
Resident
: 
"On Campus"
Staff No.
: 
"San50"
Subject
: 
"Social Studies"

I used this for loop :

onFileChange(ev) {
  this.loading.start();
  let workBook = null;


    let jsonData = null;
    const reader = new FileReader();
    const file = ev.target.files[0];
    reader.onload = (event) => {
      const data = reader.result;
      workBook = XLSX.read(data, { type: 'binary' });
      jsonData = workBook.SheetNames.reduce((initial, name) => {
        const sheet = workBook.Sheets[name];
        initial[name] = XLSX.utils.sheet_to_json(sheet);
        return initial;
      }, {});
      const dataString = JSON.stringify(jsonData);
      for(let i:number =0;i<dataString.length; i++){
        console.log(dataString[i]);
      }