keys questions

`Array.prototype.keys` returns a new Array Iterator object that contains the keys (indices) for each index in the array. It allows iteration over the array's indices. 

const arr = ['a', 'b', 'c'];
const iterator = arr.keys();
for (const key of iterator) {
  console.log(key);
}
// Output:
// 0
// 1
// 2

React's reconciliation algorithm uses keys to identify which items in a list have changed, been added, or been removed. Keys help React match elements from previous and next renders, optimizing updates and minimizing re-renders. Proper key usage ensures efficient rendering.

In JWT, public and private keys serve different purposes depending on the signing algorithm used. Private keys are used by the token issuer to sign the JWT, ensuring that the token’s authenticity can be verified. Public keys, on the other hand, are used by the recipient to verify the token’s signature. This asymmetric approach (e.g., RS256) ensures that only the issuer can sign the token, while anyone with the public key can verify its validity. This separation enhances security and allows for secure token validation across different systems.