JavaScript Arrays vs Objects

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

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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.

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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.

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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.

Comments

[izio38]

First, thanks for sharing things.
But, be precise, especially when you target beginners.

element names : keys, or accessor

There is no such undefined size. The size is defined and it's 0.

Variable pet is an array, and you talk about object.
Also, you are assigning a property on person and not on pet

[Asif Zubayer Palak]

Thank you for your valuable input, I'll update the article with your suggestions in mind <3

[Jon Randy 🎖️]

Object keys can be symbols as well as strings. With some magic, it is also possible to use arrays as keys to access object properties.

[Asif Zubayer Palak]

Amazing! Didn't know this was possible, thanks for sharing the article - learnt something new today!