Learn to Use the Switch Statement in JavaScript Like a Pro

Mastering the Switch Statement in JavaScript

In JavaScript, the switch statement is a powerful control structure designed to handle multiple conditions based on a single fixed value. This makes it a great alternative to chaining multiple if-else statements, improving readability and performance in some cases.

---

What is a Switch Statement?

The switch statement is used when you have a fixed set of values to compare against a single variable or expression. It evaluates the expression once and matches it to a case. If a match is found, the corresponding block of code is executed.

Key Features of the Switch Statement:

1. Simple Comparisons: Ideal for comparing one value against multiple fixed options.

2. Case Sensitivity: Comparisons are strict, so "Red" is not the same as "red".

3. Default Case: A default block is executed if no cases match, making it a fallback for unexpected values.

4. Break Keyword: Ensures the code exits the switch statement after executing the matching block.

---

Syntax of Switch Statement

switch(expression) {
    case value1:
        // Code block for value1
        break;
    case value2:
        // Code block for value2
        break;
    default:
        // Code block if no case matches
}

---

Example: Traffic Light Simulation

The switch statement is perfect for scenarios like traffic light controls, where fixed values (red, yellow, green) dictate specific actions.

Code:

let color = "red";

switch(color) {
    case "red":
        console.log("Stop");
        break;
    case "yellow":
        console.log("Slow down");
        break;
    case "green":
        console.log("Go");
        break;
    default:
        console.log("Broken light");
}

---

How It Works:

1. The switch evaluates the value of color.

2. It compares color to each case.

3. If a match is found, the corresponding code is executed.

4. The break statement ensures the program exits the switch block after executing the matching case.

5. If no cases match, the default block is executed.

---

Common Use Cases of Switch Statements

1. Menu Selection
   Allow users to pick from predefined options, such as app settings or commands.

2. Day of the Week Logic
   Implement actions based on the current day.

3. Error Handling
   Map specific error codes to user-friendly error messages.

---

Best Practices for Using Switch Statements

1. Use Break Statements:
   Always include break unless you intend for the cases to "fall through" (execute multiple cases in sequence).

    switch(value) {
        case 1:
            console.log("Case 1");
            break;
        case 2:
            console.log("Case 2");
            // Missing break will execute the next case as well
        case 3:
            console.log("Case 3");
    }
   

2. Provide a Default Case:
   The default block acts as a safety net for unexpected values and helps avoid silent failures.

3. Use Readable Values:
   Make the case values meaningful and consistent to avoid confusion, especially with strings.

4. Avoid Overusing:
   Use switch only when dealing with fixed comparisons. For ranges or complex conditions, if-else might be a better choice.

---

Comparison: Switch vs If-Else

---

Practice Problems

Problem 1: Grade System

Write a program to display grades based on marks:

• 90-100: "A"

• 80-89: "B"

• 70-79: "C"

• Below 70: "Fail"

    let marks = 85;
  
    switch(true) {
        case (marks >= 90 && marks <= 100):
            console.log("Grade: A");
            break;
        case (marks >= 80 && marks < 90):
            console.log("Grade: B");
            break;
        case (marks >= 70 && marks < 80):
            console.log("Grade: C");
            break;
        default:
            console.log("Grade: Fail");
    }
  

  OUT PUT

  ---

---

Problem 2: Days of the Week

Write a program to display the day of the week based on a number (1 for Monday, 7 for Sunday).

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;
    case 6:
        console.log("Saturday");
        break;
    case 7:
        console.log("Sunday");
        break;
    default:
        console.log("Invalid day");
}