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JS Fundamentals: Objects, Arrays, and Functions

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Objects & Arrays

Bonus: Map and Set

Map

A Map object is really similar to an object except that its keys can be any type, while an object only has strings as keys. It also has a nice API for working with them.

Set

A Set object is a collection of unique values. The API is really similar to the Map

Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Set may only occur once; it is unique in the Set's collection.

Example of an Object vs Array vs a Map vs a Set :

// Instantiating an instance

const myObj = {}; // object literal

const myArr = [];

const myMap = new Map(); // w/ keyword new

const mySet = new Set();

// Setting a key-value pair

myObj.key = 'value';

myObj['key'] = 'value';

myArr.key = 'value';

myArr['key'] = 'value';

myMap.set('key', 'value');

mySet.add('value');

// Check if it has a key

if (myObj.key) { console.log(true); }

myMap.has('key');

mySet.has('value');

// Getting a value

myObj.key;

myArr.includes('value');

myMap.get('key');

// Sets don't have keys, just values

// Deleting

delete myObj.key;

myMap.delete('key');

mySet.delete('value');

Read more in the docs:

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MDN Set⁠

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MDN Map⁠

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`Study Guide: Objects and Arrays`⁠

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Example of an Object vs Array vs a Map vs a Set :

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