JavaScript Control Flow: A Deep Dive

In JavaScript, control flow determines the order in which statements are executed in a program. Control flow structures allow us to make decisions, loop through data, and execute code conditionally. Let's explore these structures in depth with explanations and multiple examples for better understanding.

---

1. Conditional Statements

Conditional statements help us execute code based on certain conditions.

1.1 if Statement

The if statement executes a block of code if a specified condition evaluates to true.

Syntax:

if (condition) {
    // Code to execute if condition is true
}

Example 1:

let age = 18;
if (age >= 18) {
    console.log("You are eligible to vote.");
}

Explanation: Since age is 18, which meets the condition (>= 18), the message will be printed.

Example 2:

let temperature = 25;
if (temperature > 30) {
    console.log("It's a hot day.");
}

Explanation: The condition temperature > 30 is false, so the code inside if will not execute.

Example 3:

let num = 0;
if (num) {
    console.log("Number is non-zero");
}

Explanation: Since 0 is a falsy value in JavaScript, the condition fails, and nothing is printed.

---

1.2 if-else Statement

The if-else statement provides an alternative block of code to execute when the condition is false.

Syntax:

if (condition) {
    // Code to execute if condition is true
} else {
    // Code to execute if condition is false
}

Example 1:

let marks = 45;
if (marks >= 50) {
    console.log("Pass");
} else {
    console.log("Fail");
}

Explanation: Since marks is less than 50, the else block executes, printing "Fail".

Example 2:

let light = "red";
if (light === "green") {
    console.log("Go");
} else {
    console.log("Stop");
}

Explanation: The condition fails because light is "red", so the else block runs.

Example 3:

let loggedIn = false;
if (loggedIn) {
    console.log("Welcome!");
} else {
    console.log("Please log in");
}

Explanation: Since loggedIn is false, the else block executes.

---

1.3 if-else if-else Statement

Used for multiple conditions.

Syntax:

if (condition1) {
    // Code if condition1 is true
} else if (condition2) {
    // Code if condition2 is true
} else {
    // Code if none of the conditions are true
}

Example 1:

let score = 75;
if (score >= 90) {
    console.log("Grade: A");
} else if (score >= 75) {
    console.log("Grade: B");
} else {
    console.log("Grade: C");
}

Explanation: Since score is 75, the second condition is met, so "Grade: B" is printed.

---

2. Switch Statement

The switch statement evaluates an expression and matches it against multiple cases.

Syntax:

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

Example 1:

let day = 3;
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");
}

Explanation: Since day is 3, "Wednesday" is printed.

---

3. Looping Statements

Loops allow us to execute a block of code multiple times.

3.1 for Loop

Syntax:

for (initialization; condition; increment/decrement) {
    // Code to execute
}

Example 1:

for (let i = 1; i <= 5; i++) {
    console.log("Hello World!", i);
}

Explanation: Prints "Hello World!" 5 times.

3.2 while Loop

Syntax:

while (condition) {
    // Code to execute
}

Example 1:

let i = 1;
while (i <= 5) {
    console.log(i);
    i++;
}

Explanation: Prints numbers from 1 to 5.

3.3 do-while Loop

Syntax:

do {
    // Code to execute
} while (condition);

Example 1:

let num = 1;
do {
    console.log(num);
    num++;
} while (num <= 5);

Explanation: Runs at least once, then checks the condition.

---

4. Break and Continue

4.1 break Statement

Used to exit a loop immediately.

Example:

for (let i = 1; i <= 10; i++) {
    if (i === 5) break;
    console.log(i);
}

Explanation: Loop stops when i reaches 5.

4.2 continue Statement

Skips the current iteration and moves to the next one.

Example:

for (let i = 1; i <= 5; i++) {
    if (i === 3) continue;
    console.log(i);
}

Explanation: 3 is skipped in the loop.

---

This guide provides a deep understanding of JavaScript's control flow, helping beginners grasp the concepts through well-explained examples. Happy coding!