Consider you have an object,

const author = {
  firstName: 'Param',
  lastName: 'Harrison',
  age: 31
};

You can convert the object key-value into a nested array using the entries method,

console.log(Object.entries(author)); // [["firstName", "Param"], [...], [...]]

Using Object.entries, you can easily iterate over the key-value pair,

for (const [key, value] of Object.entries(author)) {
  console.log(`${key}: ${value}`);
}

You can play with the code example,