Function expression and Function declaration in JavaScript

In JavaScript a function can be declared in two ways.

The first way is to simply declare the function via function, immediately giving its name:

javascriptfunction func() {
  console.log('!');
}

func(); // shows '!'

The second way is to make an unnamed function and write it to some variable:

javascriptlet func = function() {
  console.log('!');
};

func(); // shows '!'

Scientifically, the first method is called Function Declaration, and the second - Function Expression.

javascriptfunction func() {
  console.log('!');
}

javascriptlet func = function() {
  console.log('!');
}