Declare JavaScript variables using var keyword

A variable is to put it simply it is a container where we can store some valuable information and access that information via the container. Think of it as a cookie jar where you store cookies and can munch them later, but it needs to be stored first right that's why we are using a jar.

There are 3 ways that we can declare a variable in javascript 

  • via keyword var
  • via keyword let
  • via keyword const

let us see how we can store the variable using var.

Var Keyword:

  • Basically var is a keyword to create a variable for storing the value.
  • Before the arrival of Ecma-Script 6, Var ruled the party of variable declaration.
  • Rather than its convenient appearance, var has some downsides to it.
  • Think of it as the content label of what is inside the cookie jar.

Example:

var pill1 = "Red Pill";
var pill2 = "Blue Pill"

console.log("Do you want the " +pill1+ " or the " +pill2+ "?")

Output:

Do you want the Red Pill or the Blue Pill?

You get the idea right?

I declared the variable and concatenated it into a print statement by passing the variable. Simple stuff!! Note: Var variables can be redeclared and reused again.

Scope Of Var:

  • The scope is the definition of where the variables can be used.
  • var is global and local scope.
  • The scope of var is global when the variable is declared outside the function where it can be accessed in the whole code.
  • Whereas when it is declared inside a function its scope is locally limited and can be used within the block of the function scope.

Example:

var x = 1;
  function foo() 
  {
    var y = 3;
    x = 2
    console.log("value of x: ", x); // output 2
    console.log("value of y: ", y); // output 3
  }
  
  foo();
  console.log("value of x: ", x); // output 2
  console.log("value of y: ", y); // output: ReferenceError: y is not defined

Here x has global scope and y has local scope. That is why you will get reference error: y is not defined when you try to access y outside the foo() function. 

Thu, 09/16/2021 - 11:45

Authored by

Ashwin is working with iVagus as a Technical Lead. He has experience in various technologies like Cypress, JavaScript, TypeScript, Rest Assured, Selenium, Cucumber, and Java.
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