function keyword

Examples

Creating an unnamed function

The following example defines an unnamed function and assigns it to x. The function returns the square of its argument:

const x = function (y) {
  return y * y;
};

 

Using a function as a callback

More commonly it is used as a callback:

button.addEventListener('click', function (event) {
  console.log('button is clicked!');
})

 

Using an Immediately Invoked Function Expression (IIFE)

An anonymous function is created and called:

(function () {
  console.log('Code runs!');
})();

// or

!function () {
  console.log('Code runs!');
}();