Js | Decision Making: | if | if Else | Else if |

Example 1: if statement

syntax:

if (condition){

  //code block 

}

Example:

             f    f   t
let temp =  #24  #25  25;


if (temp>=25);
{

console.log("it is hot outside");

} 

Example 2: if...else statement

syntax:

if (condition){

  //code block 

}
else{

   //code block 

}

Example 1:

if (temp>=25);

{

console.log("it is hot outside");

}
else{

console.log("it is cold outside");

}

Example 2:

let isRaining= #true false;

if (isRaning);
{

console.log("take an umbrella");

}
else{

console.log(" you don't need an umbrella");

}

Example 3: else if statement

syntax:

if (condition){

  //code block 

}
else if(condition){

   //code block 

}
else{

   //code block 

}

Example:

let time=14;

if (time<12){

console.log("good morning"); 

}
else if(time<18){

 console.log("good afternoon");  

}
else{

 console.log("good evening");  

}

Example 4: Nested if statements

Variables

let age= 16;
let iswithparents=true;
let idproof=true;

Decision logic

if (age>=18);{

  if(idproof);
    console.log("you can visit the mall and can able to watch the movie"); 
  } else{
     console.log("you can visit te mall"); 
  }
}else{
     if(iswithparents);
        console.log("you can visit the play area"); 
  } else{
     console.log("you are not allowed in the play are"); 
  }

}

Example:

let day=1;

if(day===1){
  console.log("monday"); 
}
else if(day===2){
  console.log("thuesday"); 
}
else if(day===3){
  console.log("wenday"); 
}
else if(day===4){
  console.log("thuesday"); 
}
else if(day===5){
  console.log("friday"); 
}
else{
console.log("in valid"); 
}

Switch Statement

syntax:

switch(vale){
  case 1:
     //code block  
      break;
  case 2:    
    //code block  
       break;
  case 3:
      //code block  
       break;
  Default:
      //code block  
       break;
}

Exmple1:

let day=3;

switch(day){

  case 1:
      console.log("monday"); 
      break;
  case 2:
      console.log("thuesday"); 
      break;
  case 3:
      console.log("wensday"); 
      break;
  case 4:
      console.log("thresday"); 
      break;
  case 5:
      console.log("friday"); 
      break;
   default:
      console.log("invalid"); 
}

output:

wensday

Exmple2:

let choice='tea';

switch(choice){

   case 'coffee':
      console.log("you choose coffee monday"); 
      break;
   case 'tea':
      console.log(" you choose tea thuesday"); 
      break;
    case 'water':
      console.log(" you choose water thuesday"); 
      break;
    default:
      console.log("invalid"); 
}

output:

you choose tea 

Ternary Operator

short hand if else

let isadmin =true;

/*if(isadmin){
  console.log("am  admin");
}
else{
   console.log("am  user");
} */

                 true        .
let userrole = isadmin ? " am admin ":" am user ";
console.log(userrole);

let mark=60;
     var        cond      if       else
let result = mark>=30 ? " pass ":" fail ";
              //true
//let result = 25>=30 ? " pass ":" fail ";

console.log(result); 

output:

pass