implicitly cast to false). Within the function, the arguments may also

be accessed through the arguments object; this provides access to all

arguments[n]), including those beyond the number of named arguments.

(While the arguments list has a .length property, it is not an instance

of Array; it does not have methods such as .slice(), .sort(), etc.)

function add7(x, y) {

if (!y) {

y = 7;

}

console.log(x + y + arguments.length);

};

add7(3); // 11

add7(3, 4); // 9

Primitive values (number, boolean, string) are passed by value. For

objects, it is the reference to the object that is passed.

const obj1 = {a : 1};

const obj2 = {b : 2};

function foo(p) {

p = obj2; // Ignores actual parameter

p.b = arguments[1];

}

foo(obj1, 3); // Does not affect obj1 at all. 3 is additional parameter

console.log(`${obj1.a} ${obj2.b}`); // writes 1 3

Functions can be declared inside other functions, and access the outer

function's local variables. Furthermore, they implement full closures by

remembering the outer function's local variables even after the outer

function has exited.

let t = "Top";

let bar, baz;

function foo() {

let f = "foo var";

bar = function() { console.log(f) };

baz = function(x) { f = x; };

}

foo();

baz("baz arg");

bar(); // "baz arg" (not "foo var") even though foo() has exited.

console.log(t); // Top

An anonymous function is simply a function without a name and can be

written either using function or arrow notation. In these equivalent

examples an anonymous function is passed to the map function and is

applied to each of the elements of the array.cite-ref-20[20]

[1,2,3].map(function(x) { return x*2;); //returns [2,4,6]

[1,2,3].map((x) => { return x*2;}); //same result

A generator function is signified placing an * after the keyword