javascript modify array item for each code example

Example 1: forEach modify array JavaScript

arr.forEach(function(part, index) {
  this[index] = "hello world";
}, arr); // use arr as this

Example 2: how to modify an array

let schedule = ['I', 'have', 'a', 'meeting', 'with'];
// adds 3 new elements to the array
schedule.splice(5, 0, 'some', 'clients', 'tommorrow');
console.log(schedule); 
// ["I", "have", "a", "meeting", "with", "some", "clients", "tommorrow"]