compound.js

// this function will return a table with data for all next years
const calculate = ({ principal, years, interest }) => {
  const rate = interest / 100;
  // the first entry is year 0—makes the logic simpler below
  const table = [[0, principal, principal, 0]];

  for (let i = 1; i <= years; i++) {
    table.push([
      i,  // year number
      table[i - 1][1] + principal * rate,  // with simple interest
      table[i - 1][2] * (1 + rate),  // with compounding interest
      table[i - 1][2] * rate  // compounding dividends this year
    ]);
  }

  // remove convenience entry for year 0
  return table.slice(1);
};