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Introduction To JavaScript

JavaScript Language has following characteristics:
  • Lightweight: Small memory footprint, easy to implement
  • Interpreted: No compilation, Instructions executed only
  • Object Oriented: Modeled around objects
  • First-class functions: Functions used as variables and parameters
  • Scripting language: Writing instructions for runtime environment
JavaScript is used for 
  • Client side web development
    • Frameworks: JQuery, AngularJs, React, EServer-side
  • Server-side web development
    • Frameworks: NodeJS, Express
Variable declaration and definition
  • Declaration: Give a name to a variable
  • Definition: Assign a value to the variable
Equal operations 
  • =: assigning value to a variable (a=30)
  • ==: check the values (doesn't consider types)
  • ===: check the values and types
Functions: 
  • no overloading
  • functions are objects
  • functional expression : assign function to variable
  • anonymous function: function with no name
Array methods
  • push(value): value is appended to the last position of an array
  • pop(): last element is removed
  • shift():first element is removed
  • unshift(value): values is appended as first element

Other Points 

  • Native JavaScript: Doesn't use any framework 
  • Doesn't associate type with variables
  • If you declare a variable and not define yet: it has undefined value
  • type of null in Javascript: object
  • For all non-zero values variable return as true.
  • JavaScript is not a class-based language: can add properties to object dynamically
  • Arrays behave like an object
  • Arguments: keyword that gets function arguments as list






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