A callback is a function passed as an argument to another function . This technique allows a function to call another function. A callback function can run after another function has finished .
Example :
let square = (num) => {
return num**2;
};
function cube(square,num) {
// return square(num)*num
// }
function quad(cube,num) {
// return cube(square,num)*num
// }
console.log(quad(cube,3))