Control Flow in JavaScript: If, Else, and Switch Explained

Hey Everyone,

In this blog, we will learn about JavaScript control flows.

When writing programs, we often need the computer to make decisions.

For example:

• If it is raining → take an umbrella

• If your marks are above 90 → grade A

• If today is Sunday → relax

Programs work the same way.
They decide which code should run based on conditions.

This idea is called control flow.

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What is Control Flow?

Control flow determines which part of the program runs and when.

Instead of executing code line by line, the program can make decisions.

Example:

let age = 18;

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

If the condition is true, the code runs.

If it is false, the code is skipped.

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The if Statement

The if statement runs code only if a condition is true.

Example

let marks = 85;

if (marks > 50) {
  console.log("You passed the exam");
}

How it works

1. Check the condition → marks > 50

2. If true → run the code inside { }

3. If false → skip it

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The if-else Statement

Sometimes we want two possible outcomes.

Example:

let age = 16;

if (age >= 18) {
  console.log("You can vote");
} else {
  console.log("You cannot vote yet");
}

Step-by-step

1. Check condition

2. If true → run if block

3. If false → run else block

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The else-if Ladder

Sometimes we have multiple conditions.

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");
}

How it runs

The program checks conditions from top to bottom.

As soon as one condition is true, the rest are skipped.

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The switch Statement

The switch statement is used when we want to check a value against multiple options.

Example: printing the day of the week.

let day = 2;

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

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

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

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

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Why a break is Important

break stops the switch after a match is found.

Without break, JavaScript continues executing the next cases.

Example without break:

let day = 1;

switch(day) {
  case 1:
    console.log("Monday");
  case 2:
    console.log("Tuesday");
}

Output:

Monday
Tuesday

Because the program falls through to the next case.

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When to Use switch vs if-else

Use Case	Best Choice
Checking ranges (marks, age, score)	if-else
Checking exact values	switch
Multiple numeric or string cases	switch
Complex conditions	if-else

Example:

marks > 90
marks < 50

These are range conditions, so if-else works better.

But:

day === "Monday"
day === "Tuesday"

Here switch is cleaner.

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Flow of if-else Decision

        Condition?
        /      \
     True      False
      |          |
   Run Code   Run Else

This is how the program decides which path to follow.

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Switch Branching Diagram

        switch(value)
             |
    ---------------------
    |    |    |    |
  case1 case2 case3 default
    |    |    |    |
   code code code code

The program jumps to the matching case.

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Practice Assignment

Try these programs in your browser console.

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1. Check Number Type

Write a program that checks if a number is:

• Positive

• Negative

• Zero

Example:

let num = -5;

if (num > 0) {
  console.log("Positive number");
} else if (num < 0) {
  console.log("Negative number");
} else {
  console.log("Zero");
}

I used if-else because we are checking different conditions.

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2. Print Day of Week

Write a program using switch.

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("Invalid day");
}

Here I used a switch because we are checking exact values.

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And now, you know what control flow is in JavaScript.

If you have any doubt or want to connect, feel free to drop a comment — I’d be happy to help.

Thanks for reading, and see you in the next blog!

Peace ✌️ and Happy Learning!

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