An example of using for loop and map as a comparison.

map-example.js

/* Map Example - Adding a property  Business */

const employeeList = [
  { name: 'Tom', job: 'Programmer' },
  { name: 'Sam', job: 'Chef' },
  { name: 'Jennifer', job: 'Digital Artist' }
];
//Create Second List to maintain original contents
const employeeList2 = JSON.parse(JSON.stringify(employeeList));
const business = 'Sun Corp';

/* For Loop */
//Create new list to contain elements
const newEmployeeList = [];
for(let i = 0; i < employeeList.length; i++) {
  const copy = JSON.parse(JSON.stringify(employeeList[i]));
  copy.business = business;
  newEmployeeList.push(copy);
}
console.log(employeeList);
console.log(newEmployeeList);

/* Map */
//List instantly created by map
const newEmployeeList2 = employeeList2.map((element) => {
  const copy = JSON.parse(JSON.stringify(element));
  copy.business = business;
  return copy;
});
console.log(employeeList2);
console.log(newEmployeeList2);