Control Statement and loops

 1)If…Else

var tomorrow = 'rain';

if(tomorrow == 'rain'){
  console.log('take a raincoat');
}else{
  console.log('No need to take a raincoat');
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
take a raincoat
PS C:UsersThe-BeastDesktopjavascript Blog> 

Example:

var tomorrow = 'no rain';

if(tomorrow == 'rain'){
  console.log('take a raincoat');
}else{
  console.log('No need to take a raincoat');
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
No need to take a raincoat
PS C:UsersThe-BeastDesktopjavascript Blog>

2) switch Statement

Example: Find the Area of circle, triangle, and rectangle?

var area = "circle" ;
var PI = 3.142, l=6, b=5, r=4;

if(area == "circle"){
  console.log("the area of the circle is : " + PI*r**2);
}else if(area == "triangle"){
  console.log("the area of the triangle is : " + (l*b)/2);
}else if(area == "rectangle"){
  console.log("the area of the rectangle is : " + (l*b));
}else{
  console.log("please enter valid data");
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
the area of the circle is : 50.272
PS C:UsersThe-BeastDesktopjavascript Blog> 

using break statement

Example:

var area = "circle" ;
var PI = 3.142, l=6, b=5, r=4;

switch(area){
  case 'circle': 
    console.log("the area of the circle is : " + PI*r**2);
    break;

  case 'triangle':
    console.log("the area of the triangle is : " + (l*b)/2);
    break;

  case 'rectangle':
    console.log("the area of the rectangle is : " + (l*b));
    break;

  default:
    console.log("please enter valid data");
}   

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
the area of the circle is : 50.272
PS C:UsersThe-BeastDesktopjavascript Blog> 

break

continue

3)While Loop Statement

Example:

var num=0;

while(num <= 10){
  console.log(num); 
  num++;
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
0
1
2
3
4
5 
6 
7 
8 
9 
10
PS C:UsersThe-BeastDesktopjavascript Blog> 

4)Do-While Loop Statement

The do…while loop is similar to the while loop except that the condition check happens at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false.

Example:

var num = 20;
do{
  console.log(num); 
  num++;
}while(num <= 10);

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
20
PS C:UsersThe-BeastDesktopjavascript Blog> 

5)For Loop

Example:

for(var num = 0; num <= 10; num++){
    console.log(num);
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
0
1 
2 
3 
4 
5 
6 
7 
8 
9 
10
PS C:UsersThe-BeastDesktopjavascript Blog> 

What are truthy and falsy values in Javascript?

we have a total of 5 falsy values in javascript.

0,” “,undefined,null,NaN,false.

Example:

if(score = 0){
    console.log("Yay, We won the game ");
}else{
    console.log("OMG, we loss the game ");
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
OMG, we loss the game 
PS C:UsersThe-BeastDesktopjavascript Blog> 

Example:

if(score = 50){
    console.log("Yay, We won the game ");
}else{
    console.log("OMG, we loss the game ");
}

output:

PS C:UsersThe-BeastDesktopjavascript Blog> node index.js        
Yay, We won the game 
PS C:UsersThe-BeastDesktopjavascript Blog> 

watch the video:https://youtu.be/KGkiIBTq0y0