JavaScript Arrays vs Objects

Know the difference between JavaScript Arrays and Objects - and know when to use them.

Difference:

Arrays use numbered indexes
Objects use named indexes

When to use:

Use Arrays when you want the keys to be numbers.
Use Objects when you want the keys to be strings.

How to use Arrays

const pets = ["cats","hamsters","dogs"];

here you are directly assigning the elements in the array.

you can access the elements in the array by

pets[0];
pets[1];
...
pets[pets.length-1];

the starting index is always 0 and ends at array.length-1.

In case of an empty arrays:

const arr = new Array();
const arr = [];

where either of the above can be used to make a new empty array.
In order to add to the array, simply arr[index] = value or arr.push(value);

const arr = new Array(size);

can be used to create an empty array of the size defined.

How to use objects

const pet = {name:"Snuffle", lastName:"Chungus", age:69};

The line above demonstrates how you can create a key-value pair. This keys can be used later to get the value.

const pet = [];
pet["name"] = "Snuffle";
pet["lastName"] = "Chungus";
pet["age"] = 69;

The codeblock above shows how key-value pairs are added to an empty object named pet.