Declaring variables in JavaScript (var, let and const)

var - properties

• Function-scoped: Variables declared with var are accessible within the entire function where they're declared, even before their line of code is reached (hoisting).
• Reassignable: Can have their values changed multiple times.
• Error-prone: Hoisting can lead to unexpected behavior if not used carefully.
• Best avoided in modern JavaScript: let and const offer better scoping and prevent common pitfalls.

let - properties

• Block-scoped: Variables declared with let are only accessible within the block of code where they're declared (e.g., within curly braces {}).
• Reassignable: Can be reassigned new values after initial declaration.
• Preferred for most variables: Offers better control over variable scope and prevents accidental overwrites.

const properties

• Block-scoped: Like let, but with an added layer of protection.
• Reassignable: Can be reassigned new values after initial declaration.
• Preferred for most variables: Offers better control over variable scope and prevents accidental overwrites.

Best Practices:

• Prefer const by default: Start with const for variables that don't need reassignment.
• Use let for variables that need to be reassigned: Employ let when values need to change.
• Avoid var in modern JavaScript: Due to its potential for scoping issues.

const name="Satish";
let marks=20;
var number = 21; 

if else and nested if else statement in JavaScript

Basic if Statement Syntax

if (condition) {
  // Code to execute if the condition is true
} 

if else Statement Syntax

if (condition) {
  // Code to execute if the condition is true
} else {
  // Code to execute if the condition is false
} 

if...else if...else Statement Syntax

if (condition1) {
  // Code to execute if condition1 is true
} else if (condition2) {
  // Code to execute if condition1 is false and condition2 is true
} else {
  // Code to execute if both condition1 and condition2 are false
} 

Exercise 1 - if else statment

let x=5
  if(x==2)
  {
      console.log('x equals 5');
  }
  else 
  {
      console.log('x is a wrong value')
  } 

Output

Exercise 2 - if...else if...else statment

let x=5
  if(x==2)
  {
      console.log('x is 2');
  }else if(x==1)
  {
      console.log('x is 1')
  }
  else
  {
      console.log('wrong value');
  } 

Output

Switch statement in JavaScript

Switch case Statement Syntax

switch (expression) {
  case value1:
    // Code to execute if expression matches value1
    break;
  case value2:
    // Code to execute if expression matches value2
    break;
  // ... more cases
  default:
    // Code to execute if expression doesn't match any of the cases
}

Exercise 1 - Switch Case with Integer

let x=2
  switch(x)
  {
      case 1:
          console.log('x is 1');
          break;
      case 2:
          console.log('x is 2');
          break;
      default:
          console.log('x is not good value');
          break;
  }

Output

Exercise 2 - Switch Case with Character Input

let x='c'
  switch(x)
  {
      case 'a':
          console.log('x is a');
          break;
      case 'c':
          console.log('x is c');
          break;
      default:
          console.log('x is not good value');
          break;
  }

Output

Simple for loop in JavaScript

Syntax for simple for loop

for (initialization; condition; increment/decrement) {
  // Code to be executed repeatedly
}

Exercise 1 - Use simple for loop and print the numbers from 0 to 4

let i=0
  for(i=0;i<5;i++)
  {
      console.log(i);
  }

Output

While loop in JavaScript

Syntax for while loop

while (condition) {
  // Code to be executed repeatedly
}

Exercise 1 - Use simple while loop and print the numbers from 0 to 4

let x=0; 
  while (x<5)
  {
      console.log(x);
      x++ 
  }

Output

do While loop in JavaScript

Syntax for do while loop

do {
  // Code to be executed at least once
} while (condition); 

Exercise 1 - Use simple do while loop and print the numbers from 0 to 4

let x=0; 
  do
  {
     console.log(x);
     x++
  }while(x<5)

Output

Declaring Arrays in JavaScript

Syntax for Array Declaration

// 1. Using square brackets:
  let myArray = [];  // Empty array
  let numbers = [1, 2, 3, 4, 5];  // Array with initial values
  
  // 2. Using the Array constructor:
  let colors = new Array("red", "green", "blue");

Exercise 1 - Printing the elements inside an array using a simple for loop

const k = [1,2,3,4,5,6]
  for(let i=0;i<k.length;i++)
  {
      console.log(k[i]);
  }

Output

Exercise 2 - Printing elements inside an array using for in loop

const k = [1,2,3,4,5,6]
  for(var j in k)
  {
      console.log(k[j]);
  }

Output

Exercise 3 - Printing elements inside an array using for of loop

const k = [1,2,3,4,5,6]
  for(var j of k)
  {
      console.log(j);
  }

Output