JavaScript Control Flow

Programming is not just about writing instructions — it is also about making decisions.

In real life, we make decisions every day.

Example:

• If it rains → take an umbrella

• If you pass the exam → celebrate

• If it is Sunday → relax

Programming works in the same way.
This concept is called Control Flow.

What is Control Flow?

Control flow defines how a program decides which code should run and when.

It allows programs to:

• make decisions

• execute different code blocks

• control the order of execution

JavaScript provides several ways to control program flow:

1. if statement

2. if-else statement

3. else if ladder

4. switch statement

1. if Statement

The if statement runs a block of code only when a condition is true.

Syntax:

if(condition){
   // code runs if condition is true
}

Example:

let age = 20;

if(age >= 18){
   console.log("You can vote");
}
//You can vote

Explanation:

Step 1 → Check condition age >= 18
Step 2 → If true, run the code inside {}

Real Life Example

If a student scores above 40 marks, they pass.

let marks = 50;

if(marks >= 40){
   console.log("You passed the exam");
}
// You passed the exam

2. if-else Statement

Sometimes we need two possible outcomes.

Example: Pass or Fail.

Syntax:

if(condition){
   // runs if condition is true
}
else{
   // runs if condition is false
}

Example:

let marks = 35;

if(marks >= 40){
   console.log("Pass");
}else{
   console.log("Fail");
}
//Fail

Explanation:

Program checks condition → false → runs else block.

3.Else If Ladder

When there are multiple conditions, we use else if.

Example: grading system.

let marks = 75;

if(marks >= 90){
   console.log("Grade A");
}
else if(marks >= 75){
   console.log("Grade B");
}
else if(marks >= 50){
   console.log("Grade C");
}
else{
   console.log("Fail");
}
//Grade B

The program checks conditions one by one from top to bottom.

As soon as one condition becomes true, the remaining conditions are skipped.

4.Switch Statement

When there are many specific values, switch can be cleaner than multiple if-else.

Syntax:

switch(value){
   case option1:
       // code
       break;

   case option2:
       // code
       break;

   default:
       // code
}

Example: Day of the week

let day = 3;

switch(day){
   case 1:
      console.log("Monday");
      break;

   case 2:
      console.log("Tuesday");
      break;

   case 3:
      console.log("Wednesday");
      break;

   case 4:
      console.log("Thursday");
      break;

   case 5:
      console.log("Friday");
      break;

   default:
      console.log("Weekend");
}
//Wednesday

#Why break is Important

The break statement stops the switch from continuing to the next case.

Example without break:

let day = 1;

switch(day){
   case 1:
      console.log("Monday")

   case 2:
      console.log("Tuesday")
}
//Output: Monday
//        Tuesday
//Because there was no break, the program continued to the next case.

Example with break:

let day = 4;

switch(day){
   case 1:
      console.log("Monday");
      break;

   case 2:
      console.log("Tuesday");
      break;

   case 3:
      console.log("Wednesday");
      break;

   case 4:
      console.log("Thursday");
      break;

   case 5:
      console.log("Friday");
      break;

   case 6:
      console.log("Saturday");
      break;

   case 7:
      console.log("Sunday");
      break;

   default:
      console.log("Invalid Day");
}

Explanation:

We used switch because we are checking fixed values from 1 to 7.

Final Thoughts

Control flow allows programs to think and make decisions.

Key points:

• if → run code if condition is true

• if-else → choose between two options

• else if → handle multiple conditions

• switch → handle many fixed values

Once you understand control flow, you can start building real logic in programs.

Happy Coding 🚀