4-functions.md

Functions

Functions in JavaScript behave very similar to other C-like languages.

// A named function statement
function doNothing1 () {}

Everything in JavaScript is an object or primitive type. Even Array basically is an extension of Object. Even Function is a kind of Object. This means all functions are values.

// An implicitly-named function
var doNothing2 = function () {}
// An implicitly-named arrow function
const doNothing3 = () => {}

Also keep in mind function arguments can be omitted, but they will always be applied in order.

function list3Things (a, b, c) {
  console.log(a);
  console.log(b);
  console.log(c);
}

list3Things('a', 'b', 'c');
// a
// b
// c

list3Things('a', 'c');
// a
// c
// undefined

It is not smart enough to know what values are meant to pair with which parameters. If you see vendor libraries "fix" method calls with missing parameters, that is not JavaScript but a developer helping you out.