Callbacks and Higher-Order Functions

const numbers = [1, 2, 3, 4, 5, 6];
const evens = numbers.filter(function(num) {
  return num % 2 === 0;
});
console.log(evens);

[1, 3, 5]
[2, 4, 6]
The output is [2, 4, 6]. The filter() method creates a new array with all elements that pass the test implemented by the provided callback function. The callback in this example checks if a number is even by testing if the remainder when divided by 2 equals 0. Only the even numbers (2, 4, and 6) pass this test and are included in the resulting array. filter() is a higher-order function that doesn't modify the original array but returns a new array with the filtered elements.
[]
[1, 2, 3, 4, 5, 6]