CODE EXAMPLE FOR JAVASCRIPT

array-object loop

const data = [
  { name: 'John', age: 30, group: 'A' },
  { name: 'Mary', age: 25, group: 'B' },
  { name: 'Mike', age: 20, group: 'A' },
  { name: 'Jane', age: 15, group: 'C' },
  { name: 'Peter', age: 25, group: 'B' }
];

// for...in loop
for (const index in data) {
  console.log(index, data[index]);
}