Javascript and Callback function - callback

Question

I’m a newbie in programming language and I’m learning Javascript. I’m trying to understand the concept of callback function. I realized that callback is intended a function passed as parameter, but when does it call?
In the below examples I used a classic approach to write functions and then I tried to use the arrow function. The callback is done() function, in the first example it is called after the parent function, in the second one after.
What is the reason? Can you give me an explanation? Thank you so much for the feedback
Example no. 1
function done(){
console.log("Done");
}
function increment(num, callBack){
for(var i = 0; i <= num; i++){
console.log(i);
}
return callBack();
}
increment(10, done);
Example no. 2
const done = () => {
console.log("Done");
}
const increment = (num, done) => {
for (var i = 0; i <= num; i++) {
console.log(i);
}
}
increment(10, done());

Answer 1

To use callback you need to specify that there'll be a callback function as a argument, and you need to call that somewhere in the parent function like this, and that's when it will be called:
function someFunction(callback){
//Do something if needed...
callback() //callback(someParameter) if you want to pass some parameter to the callback func
//Do something if needed...
}
In your 2nd example, it's actually not a proper way of using callback function because you did not call the callback function inside parent function. You can modify it to to make it work as 1st example like this:
const increment = (num, done) => {
for (var i = 0; i <= num; i++) {
console.log(i);
}
done(); //call the callback function
}
increment(10, done); //just pass the name of callback func, not call it like you did "done()"