CODE EXAMPLE FOR JAVASCRIPT

For-in loop

const obj = {
  a: 1,
  b: 2,
  c: 3,
};

// Long-hand
const keys = Object.keys(obj);
for (let i = 0; i < keys.length; i++) {
  const key = keys[i];
  const value = obj[key];
  // ...
}

// Short-hand
for (const key in obj) {
  const value = obj[key];
  // ...
}