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Conditional (If-Else)

Q: When should you use 'else if' instead of just another 'if'?

Answer: You use 'else if' when the conditions are mutually exclusive. Once one condition in an if-else if-else chain is met, the rest are skipped, which is more efficient than checking multiple independent 'if' statements..

Q: How does the ternary operator work?

Answer: It takes three operands: a condition followed by a question mark (?), an expression to execute if the condition is true followed by a colon (:), and finally the expression to execute if the condition is false..

Q: Which values are considered 'falsy' in a condition?

Answer: The falsy values are false, 0, -0, empty string (""), null, undefined, and NaN..

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Expert Answer & Key Takeaways

Mastering Conditional (If-Else) is essential for high-fidelity technical architecture and senior engineering roles in 2026.

JavaScript Conditional Statements

Conditional statements are used to perform different actions based on different conditions. In 2026, efficient branching logic is key to writing clean and performant applications.

1. The `if` Statement

Use the if statement to specify a block of JavaScript code to be executed if a condition is true.

if (hour < 18) {
  greeting = "Good day";
}

2. The `else` Statement

Use the else statement to specify a block of code to be executed if the condition is false.

if (hour < 18) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}

3. The `else if` Statement

Use the else if statement to specify a new condition if the first condition is false.

if (time < 10) {
  greeting = "Good morning";
} else if (time < 20) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}

4. Ternary Operator (Condition ? True : False)

The ternary operator is a shorthand for if-else and is highly used in modern React and Next.js applications in 2026.

let greeting = (hour < 18) ? "Good day" : "Good evening";

5. Truthy and Falsy in Conditions

In JavaScript, you don't always need to compare explicitly to true or false. Any value can be used as a condition.

let x = 10;
if (x) {
  // This executes because 10 is 'truthy'
}

let y = 0;
if (y) {
  // This does NOT execute because 0 is 'falsy'
}

[!IMPORTANT] Remember the falsy values: false, 0, -0, "", null, undefined, and NaN. Everything else is truthy.

Conditional (If-Else)

Expert Answer & Key Takeaways

JavaScript Conditional Statements

1. The `if` Statement

2. The `else` Statement

3. The `else if` Statement

4. Ternary Operator (Condition ? True : False)

5. Truthy and Falsy in Conditions

Top Interview Questions

?Interview Question

?Interview Question

?Interview Question

Course4All Engineering Team

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Conditional (If-Else)

Expert Answer & Key Takeaways

JavaScript Conditional Statements

1. The if Statement

2. The else Statement

3. The else if Statement

4. Ternary Operator (Condition ? True : False)

5. Truthy and Falsy in Conditions

Top Interview Questions

?Interview Question

?Interview Question

?Interview Question

Course4All Engineering Team

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1. The `if` Statement

2. The `else` Statement

3. The `else if` Statement