How to properly call a callback function?

Question

JavaScript

Good evening everyone!
I have a theoretical question, I can not understand the syntax and logic of using callback functions. Everything that I googled - talks about the same examples and does not give me an understanding of the following points:

var func = function(callback){
    var name = "Max";
    callback(name);
  };
func(function(n){
    console.log("Hi " + n);
  });

1) An anonymous function is passed to the funk variable with an argument in the form of a callback function. So? Farther.
In the main function: 1) the name variable is declared 2) the callback function is called with the name argument...
But it hasn't been described yet, has it? Or is it not a function call, but something else? What?
2) Call func(); with a callback in the form of an anonymous function with an argument n. When printed to the console, it turns out that n got the value of the name variable from the func function declaration. What does this follow from? How are n and name related?
Thanks in advance for your replies. The question is pretty confusing, but that's the question, not the answer.

Answer 1

Functions Have Parameters
When you call a callback function, it's the same as calling fn with parameters like this.
Your case

function fn (a, b, c) { alert(a, b, c) }

function foo (callback) { 
   var a = 1, b = 2, c = 3
   callback(1, 2, 3) // равносильно fn (1, 2, 3)
}

foo(fn)

It is not necessary to pass an anonymous function, any function.
Summary: You would first deal with the functions.
Read this, for example: https://learn.javascript.ru/function-basics

Answer 2

Hm... A function can be written into a variable, into anything. Imagine an example:

function a(name) {
    alert(name);
}
a("Vanya");

Look - the string has not yet been created, but it is already used in the function! Same with callback:

function a(name, callback) {
    alert(name);
    callback(name);
}
a("Vanya", function(name) { console.log(name); });

Look, it's almost the same here. Perhaps you are confused by the callback function ? Then here's the answer - everything in js is represented by variables and properties, even functions. Thus, the function in the callback variable is called ! And callback is a variable that contains an anonymous function.
Also, as Yaroslav Lyzlov already noted , you can pass not only an anonymous function.

Answer 3

Here, creatively rethought, everything seems to be clear and everything works:

function fuck(girl, boy, callback){
  var hookUp;
  if(girl >=18 && boy >=18){
    hookUp = true;
  }else hookUp = false;	
  callback(hookUp);
}
fuck(19,30, function(hookUp){
  if(hookUp){
    console.log("You're welcome!");	
  }else console.log("No way!!!");
});