callback

 // A callback is a function passed as

The default syntax for arrow function is

() => {}

This can be used as callbacks

For example if we want to print all elements in an array [1,2,3,4,5]

without arrow function, the code will look like this

[1,2,3,4,5].forEach(function(x){
                 console.log(x);
            }

With arrow function, it can be reduced to

[1,2,3,4,5].forEach(x => console.log(x));

Here the callback function function(x){console.log(x)} is reduced to x=>console.log(x)

// an argument to another function

// This technique allows

// a function to call another function

// A callback function can run after 

//another function has finished

function f1(){

    f2();

    console.log("hello");

    

}

function f2(){

    console.log("good morning");

}

f1();

....................................

function f1(a,b,callback){

   console.log( callback(4,6));

}

function sum(x,y){

return x+y;

}

f1(5,4,sum);