JavaScript - At a glance

When I started learning JavaScript, I was kind of perplexed, where should I start, what should I learn first, how many concepts does JavaScript really have? Though there were a lot of articles answering those questions, I think they are a bit verbose. And I found a little hard to find the concrete key points from there. So I made a simple note which a beginner may follow and kept it concise so that one can easily extract the key points or terminologies and start researching right away.

Creation history

• Creator - Brendan Eich
• Created at - 1995
• Original name - LiveScript
• Renamed - JavaScript

First release

• 1996 with Netscape

Version history

• 1st : 1996
• 2nd : 1998
• 3rd : 1999
• 4th : Abandoned
• 5th : 2009
• 6th : 2015

Host environments

• Web Browser
• Adobe Acrobat
• Adobe Photoshop
• SVG images
• Yahoo's Widget engine
• Node.js
• CouchDB
• GNOME

Language type

• Multi-paradigm
• Dynamic
• OOP
• Object prototypes
• Functional programming

Types

• Number
• String
• Boolean
• Object
  • Function
  • Array
• Symbol
• null
• undefined

Variable

• Declaration
  • var, let, const

Operators

• Assignment (=)
• Addition/Concatenation (+)
• Substraction (-)
• Multiplication (*)
• Division (/)
• Modulus (%)
• Increment (++)
• Decrement (--)
• Comparison (>, <, <=, >=)
• Equality/Not equality (===, ==, !==, !=)
• And (&&)
• Or (||)
• Bitwise

Control structures

• if/else
• switch
• for
• while
• do-while
• for-in
• for-of

Truthy and Falsy

• Falsy
  • false, 0, '', NaN, null, undefined
• Truthy
  • Everything else which are not falsy, are Truthy

Built in objects

• Math
• Error
• RegEx
• Date
• Object
• String
• Number
• Array
• Boolean
• JSON
• Promise

Number

• Most used APIs
  • Number.toString()
  • Number.parseInt()
  • Number.parseFloat()
  • Number.isNaN()
  • Number.isFinite()
  • Number.isInteger()
  • Number.toExponential()
  • Number.toFixed()

String

• Most used APIs
  • String.prototype.length
  • String.prototype.charAt()
  • String.prototype.fromCharCode()
  • String.prototype.concat()
  • String.prototype.repeat()
  • String.prototype.search()
  • String.prototype.indexOf()
  • String.prototype.lastIndexOf()
  • String.prototype.replace()
  • String.prototype.fromCharCode()
  • String.prototype.toLowerCase()
  • String.prototype.toUpperCase()
  • String.prototype.substring()

Object

• Most used APIs
  • Object.assign()
  • Object.create()
  • Object.defineProperty()
  • Object.defineProperties()
  • Object.entries()
  • Object.freeze()
  • Object.hasOwnProperty()
  • Object.isPrototypeOf()
  • Object.assign()
  • Object.keys()
  • Object.getPrototypeOf()
  • Object.getOwnPropertyNames()
  • Object.getOwnPropertyDescriptor()
  • Object.getOwnPropertyDescriptors()

Function

• Most used APIs
  • Function.name
  • Function.prototype
  • Function.call()
  • Function.bind()
  • Function.apply()

Array

• Most used APIs
  • Array.length
  • Array.isArray()
  • Array.prototype.pop()
  • Array.prototype.push()
  • Array.prototype.shift()
  • Array.prototype.map()
  • Array.prototype.filter()
  • Array.prototype.reduce()
  • Array.prototype.concat()
  • Array.prototype.join()
  • Array.prototype.include()
  • Array.prototype.splice()
  • Array.prototype.forEach()
  • Array.prototype.indexOf()
  • Array.prototype.find()
  • Array.prototype.findIndex()
  • Array.prototype.slice()

Those are not all concepts JavaScript has. Those are basics and you can follow them while starting with it rather than roaming here and there aimlessly. There is a lot of stuff inside there. But if you go through the above stuff and keep digging, you may understand yourself what more inside there what should study next.
For deep dive - https://developer.mozilla.org/en-US/docs/Web/JavaScript