Forem: catch(js)

02 - Primitive and Non-Primitive Data Types in Javascript

catch(js) — Thu, 02 Jul 2020 07:58:20 +0000

Data types in js is broadly classified into 2 types:

Primitive types :

Type	Description
string	Used for denoting strings
number	Used for denoting integers or floating-point
bigint	Used for denoting whole numbers larger than 2⁵³ - 1
boolean	Used for denoting true or false
undefined	Used for denoting an unassigned value
symbol	Used for denoting unique identifiers
null	Used for denoting an intentional absence of a value

Non-primitive types :

Type	Description
object	Used for denoting complex data structure with a collection of properties and methods

All JavaScript values, except primitives, are objects.

Mutable values are those which can be modified after creation
Immutable values are those which cannot be modified after creation

So the fundamental difference between primitive and non-primitive is that primitive values are immutable and non-primitive values are mutable and Primitives are stored by value while Non-Primitive (objects) are stored by reference.

It is important to note here that the variable in which the primitive value is stored can still be reassigned a new value as shown in Example 1, but the existing value can not be changed as shown in Example 2. A primitive value can be replaced, but it can't be directly altered.

Example 1

let string = 'hello world'
string = 'this is a string';
console.log(string) // Output -> 'this is a string'

Example 2

let string = 'this is a string'
string[0] = 'T'
console.log(string) // Output -> 'this is a string.'

How do primitive values such as strings have toUpperCase() method?

There are many things one would want to do with primitive values(number, string, etc...) such as finding the length of string, converting a string to uppercase or lowercase, and many more...
Thus Javascript allows us to work with Primitive as if they are objects. In order for that to work, a special “object wrapper” that provides the extra functionality is created because of which we can access those methods and then is destroyed after the work.

Primitives except null and undefined provide many helpful methods
The “object wrappers” are different for each primitive type and are called: String, Number, Boolean and Symbol. Thus, they provide different sets of methods.

Example 3

let str = "javascript";
console.log( str.toUpperCase() ); // JAVASCRIPT

In Example 3 when we accessing its property, a special object is created which has useful methods, like toUpperCase().
That method runs and returns a new string. After which
the special object is destroyed, leaving the primitive str alone.

How are Non-primitive values mutable

Example 4

let arr = [ 'one', 'two', 'three' ];
arr[0] = 'ONE';
console.log(arr) // Output -> [ 'ONE', 'two', 'three' ]

In example 4 we are mutating the state of variable arr and changing the value itself as value at index 0 is changed from one to ONE

The typeof operator

typeof operator returns a string that tells the type of a JavaScript variable.

typeof "hello" // "string"

typeof 0 // "number"

typeof 1n // "bigint"

typeof true // "boolean"

typeof undefined // "undefined"

typeof Symbol("id") // "symbol"

typeof {} // "object"

typeof null // "object"

Why is null an object

This is a bug which states that null is an object and one that unfortunately can’t be fixed because it would break the existing code of people.

01 - Introduction to JavaScript | History | Current status

catch(js) — Tue, 30 Jun 2020 08:55:05 +0000

What is JavaScript

Javascript is popularly known as a powerful scripting language for controlling web pages.

Tho' It was originally designed as a scripting language for websites but it has evolved so much since then that now javascript is used everywhere. Through javascript, you can build web applications, create APIs, build mobile applications, even do Machine Learning, and what not...

History of javascript

In September 1995, a Netscape programmer named Brandan Eich developed a scripting language in just 10 days which was named Mocha.
Then it was named LiveScript and later javascript which became one of the most popular programming languages.

What is ECMAScript

ECMAScript provides the rules, details, and guidelines that a scripting language must follow to be considered ECMAScript compliant. Thus javascript is a scripting language which is based on ECMAScript and follows the ECMAScript specification. Releasing a new edition of ECMAScript with new features does not mean that JavaScript will also be having those new features immediately. Javascript might take some time to adopt those new ECMAScript features.

Here is a list of ECMAScript Editions:

Version	Year
ES1	1997
ES2	1998
ES3	1999
ES4	Never Released
ES5	2009
ES6	2015
ES7	2016
ES8	2017
ES9	2018

Current Status of Javascript

Javascript has a very large ecosystem and most importantly a great community. Tho' Javascript has a simple syntax and is easy to start with but is almost impossible to master. it is quite a funny language with lots of tricky parts which we are gonna cover in our upcoming articles.

Catch(js) Introduction

catch(js) — Mon, 29 Jun 2020 07:29:45 +0000

What is Catch(js) ?

Catch(js) is a series of articles that go from basics to advanced topics in javascript with simple yet detailed explanations.

Content of articles?

The articles will be focussed on the core mechanics of javascript and some of the topics that will be covered are :

this
Primitive and non-primitive data types
Coercion
What is 'use strict'
function expression and function declaration
Arrow functions vs regular function
Objects
Array and Object methods
Garbage collection
Event loop
Prototypes
Error handling
IIFE
Scope
Closures
The Module Pattern
Class-based syntax
Hoisting
Currying
Memoization
apply, call, and bind methods
Asynchronous JS
Callbacks
Promises
Async & Await
Generators

And many more topics...

What to expect from this series?

The series of articles will help people increase their expertise in javascript, As the articles will be short and concise one can also brush up the topics through this series for interviews.

Authors of Catch(js):

You can reach us at any time for doubts regarding the topics covered or if you want us to write about a particular topic.