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Javascript: Data Types and Variables


JAVASCRIPT

  • Programming language type: High level, Low level
  • Procedure, Functional, Structure programming language
  • Javascript mix
  • Javascript prototype-based, follow inheritance, the class implementation
  • Javascript is used for user interaction
  • Javascript disabled in browser: content setting, javascript block and see the UI Javascript asynchronous Javascript is a loosely typed programming language
  • Framework: used to build the whole application
  • Library: certain task purpose
  • Heroku Deployment
  • Build Frontend and Backend independent application
  • Paypal: developed using Node js and Express js

Data Types

1. String:
single-quote or double quote 'Nepal', "Nepal"
best practice -> "Country('Nepal')"

2. Number:
integer, double, float
123, 12.234

3. boolean true false
4.Object 
eg: {
     name: 'Ram',
     addr: 'ktm'
}

 5. array
eg: [{
     name: 'Ram',
     addr: 'ktm'

}]

6. undefined
variable declaration without value

7. null
Non declared variable

Variable : 

declarationa and memory allocate
es5, es6 (ECMAScript : javascript standard, manage javascript version)

es5 variable declaration -> eg: var const
var ram;
console.log('ram is' , ram); undefined

es6 variable declaration -> eg: let const

####Javascript is loosely typed programming language####

Example:
var a;

a ='Welcome to USA'; string
a = true; boolean value
a = 123; number
a = undefined; undefined
a = null; null
console.log('a is now' , a); displaying datatype

 # Logical Operator
Logical OR (one needs to be true)
Logical AND (both true)
Logical NOT (true -> invertor (false))

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