What is a callback function in JavaScript with an example?

A function passed as an argument to another function is called a callback function and this technique allows a function to call another function. A callback function gets executed after the execution of another function gets finished.

Example

function isOdd(number) {
  return number % 2 != 0;
}
function filter(numbers, fn) {
  let results = [];
  for (const number of numbers) {
    if (fn(number)) {
      results.push(number);
    }
  }
  return results;
}
let numbers = [1, 2, 4, 7, 3, 5, 6];
console.log(filter(numbers, isOdd));

Answer // [ 1, 7, 3, 5 ]

The benefit of using this feature is that you can wait for the result of a previous method call and then execute another method call.