anonymous function javascript

                                     1 int function (int a) {
 2   return a + 3;
 3 }
 4 
 5 class Functor {
 6   public:
 7     int operator()(int a) {
 8       return a + 3;
 9     }
10 };
11 
12 int main() {
13   auto lambda = [] (int a) { return a + 3; };
14 
15   Functor functor;
16 
17   volatile int y1 = function(5);
18   volatile int y2 = functor(5);
19   volatile int y3 = lambda(5);
20 
21   return 0;
22 }

                                    // There are several definitions

// Non-anonymous, you name it
function hello() { /* code */ }
// Call as usual
hello()

// The myriad of anonymous functions

// This is actually anonymous
// It is simply stored in a variable
var hello = function() { /* code */ }
// It is called the same way
hello()

// You will usually find them as callbacks
setTimeout(function(){ /* code */ }, 1000)
// jQuery
$('.some-element').each(function(index){ /* code */ })

// Or a self firing-closue
(function(){ /* code */ })()

                                    //Anonymous function; It's not assigned to an indentifier

Array.forEach((arguments) => {
	//This is an anonymous function
})

function forEach(arguments) {
	//This is NOT an anonymous function
}

                                    // ES5
var multiplyES5 = function(x, y) {
  return x * y;
};

// ES6
const multiplyES6 = (x, y) => { return x * y };

                                    // Arrow functions
// ES6 introduced arrow function expression that provides a shorthand for declaring anonymous functions:

// For example, this function:

let show = function () {
    console.log('Anonymous function');
};
// Code language: JavaScript (javascript)
// … can be shortened using the following arrow function:

let show = () => console.log('Anonymous function');
let show = (variable) => { /* code */ }
// Code language: JavaScript (javascript)
// Similarly, the following anonymous function:

let add = function (a, b) {
    return a + b;
};
// Code language: JavaScript (javascript)
// … is equivalent to the following arrow function:

let add = (a, b)  => a + b;