JSFiddle - React, Tailwind, and code Playground

JavaScript

// Declare input and a new array
let input = undefined;
const arr = [];

while (input !== 'done') {

  // Get the input
  input = prompt('Enter some text');

  // If input is not `done` push the input
  // to the array
  if (input !== 'done') arr.push(input);
}

// If the array has some elements
// In your working code remove this line, and
// uncomment out the next
// if (arr.length) console.log(JSON.stringify(arr));
if (arr.length) saveData(arr);

function saveData(arr) {
  localStorage.setItem('data', JSON.stringify(arr));
}