// With the constructor

myArray = new Array(0, 1, 2, 3, 4, 5); // length of 6

Arrays are implemented so that only the defined elements use memory;

they are "sparse arrays". Setting myArray[10] = 'someThing' and

myArray[57] = 'somethingOther' only uses space for these two elements,

just like any other object. The length of the array will still be

reported as 58. The maximum length of an array is 4,294,967,295 which

corresponds to 32-bit binary number (11111111111111111111111111111111)2.

One can use the object declaration literal to create objects that behave

much like associative arrays in other languages:

const dog = {color: "brown", size: "large"};

dog["color"]; // results in "brown"

dog.color; // also results in "brown"

One can use the object and array declaration literals to quickly create

arrays that are associative, multidimensional, or both. (Technically,

JavaScript does not support multidimensional arrays, but one can mimic

them with arrays-of-arrays.)

const cats = [{color: "brown", size: "large"},

{color: "black", size: "small"}];

cats[0]["size"]; // results in "large"

const dogs = {rover: {color: "brown", size: "large"},

spot: {color: "black", size: "small"}};

dogs["spot"]["size"]; // results in "small"

dogs.rover.color; // results in "brown"

A Date object stores a signed millisecond count with zero representing

1970-01-01 00:00:00 UT and a range of ±108 days. There are several ways

of providing arguments to the Date constructor. Note that months are

zero-based.

time/date.

2010-Mar-01 00:00:00

representing 2010-Mar-01 14:25:30

String.

Methods to extract fields are provided, as well as a useful toString:

const d = new Date(2010, 2, 1, 14, 25, 30); // 2010-Mar-01 14:25:30;

// Displays '2010-3-1 14:25:30':

d.getDate() + ' '

+ d.getHours() + ':' + d.getMinutes() + ':' + d.getSeconds());