Learning Java Script Basics-Part 1

I have started learning Javascript to work on Cypress/Webdriver IO for Automation of Angular applications. I will share the key points so that it may be useful for others to learn/revise.

So in part 1 lets start with some basics.

Note: For complete repo visit https://github.com/Jadalaajay16/Javascript.git and choose master branch.

console.log(“Hello World”)

//JavaScript accepts both double and single quotes:

let a=4

console.log(a) //op: 4

console.log(typeof(a)) //op:number

//JavaScript has only one type: numbers (not like other languages contains float,doublt,int etc..)

//Numbers can be written with, or without decimals:

let b = 234.6

console.log(typeof(b)) //op:number

var c = “Rahul Shetty”

console.log(typeof(c)) //op:string

let required = true

console.log(typeof(required)) //op:boolean

//null and undefined

// let c = a+b ( it do not work -we cannot redeclare variable with let keyword but possible with var)

c = a+b // reassigning is allowed with let

//var c=a+b (this is also allowed)

console.log(c) //op:238.6

console.log(!required) //op: false

//var:both redeclaring and reassigning works

//let: redeclaring not allowed, reassigning is allowed

//const: both redeclaring and reassigning does not work

//instanceof: Returns true if an object is an instance of an object type

//JavaScript has dynamic types. This means that the same variable can be used to hold different data types:

let x; // Now x is undefined

x = 5; // Now x is a Number

x = “John”; // Now x is a String

console.log(x) //op: John

JavaScript Objects: JavaScript objects are written with curly braces {}.

Object properties are written as name:value pairs, separated by commas.

const person = {firstName:”John”, lastName:”Doe”, age:50, eyeColor:”blue”};

let car; // Value is undefined, type is undefined

//Any variable can be emptied, by setting the value to undefined. The type will also be undefined.

car = undefined; // Value is undefined, type is undefined

//An empty value has nothing to do with undefined. An empty string has both a legal value and a type.

let car = “”; // The value is “”, the typeof is “string”

Please do comment if you find any improvements/corrections/clarifications to improvise this article.