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Booleans & Logic

Q: What is the difference between 'true' and Truthy?

Answer: 'true' is the literal Boolean value. 'Truthy' refers to a non-boolean value that evaluates to true when converted to a boolean (for example, any non-zero number or non-empty string)..

Q: Which values evaluate to 'false' in JavaScript?

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

Q: Why should you avoid using 'new Boolean()'?

Answer: Using 'new Boolean()' creates a Boolean object instead of a primitive value. This can cause unexpected behavior during comparisons and is generally slower and less memory-efficient..

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Expert Answer & Key Takeaways

Mastering Booleans & Logic is essential for high-fidelity technical architecture and senior engineering roles in 2026.

JavaScript Booleans

A JavaScript Boolean represents one of two values: true or false. In 2026, Booleans are the core of all conditional logic, allowing programs to make decisions based on data.

1. The Boolean() Function

You can use the Boolean() function to find out if an expression (or a variable) is true.

Boolean(10 > 9);        // Returns true

Or even easier:

(10 > 9);              // Also returns true
10 > 9;                // Also returns true

2. Comparisons and Conditions

Booleans are typically the result of comparison operations:

let x = 0;
Boolean(x == 10);      // Returns false

3. Everything With a "Value" is True

In JavaScript, almost any value that "exists" evaluates to true (Truthy).

Boolean(100);          // true
Boolean(3.14);         // true
Boolean(-15);          // true
Boolean("Hello");      // true
Boolean("false");      // true
Boolean(7 + 1 + 3.14); // true

4. Everything Without a "Value" is False

The Boolean value of any value that does not "exist" is false (Falsy). The Boolean value of 0 (zero) is false:

let x = 0;
Boolean(x);            // false

The Boolean value of -0 (minus zero) is false:

let x = -0;
Boolean(x);            // false

The Boolean value of "" (empty string) is false:

let x = "";
Boolean(x);            // false

The Boolean value of undefined is false:

let x;
Boolean(x);            // false

The Boolean value of null is false:

let x = null;
Boolean(x);            // false

The Boolean value of NaN is false:

let x = 10 / "H";
Boolean(x);            // false

5. Booleans as Objects

Normally JavaScript booleans are primitive values created from literals. But booleans can also be defined as objects with the keyword new. However, you should never create Booleans as objects. It complicates the code and slows down execution speed.

let x = false;
let y = new Boolean(false); 

// typeof x returns boolean
// typeof y returns object

[!IMPORTANT] Comparing two JavaScript objects always returns false (even if they have the same value).

Booleans & Logic

Expert Answer & Key Takeaways

JavaScript Booleans

1. The Boolean() Function

2. Comparisons and Conditions

3. Everything With a "Value" is True

4. Everything Without a "Value" is False

5. Booleans as Objects

Top Interview Questions

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Course4All Engineering Team

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Booleans & Logic

Expert Answer & Key Takeaways

JavaScript Booleans

1. The Boolean() Function

2. Comparisons and Conditions

3. Everything With a "Value" is True

4. Everything Without a "Value" is False

5. Booleans as Objects

Top Interview Questions

?Interview Question

?Interview Question

?Interview Question

Course4All Engineering Team

Explore More javascript

Operators

Arithmetic

Assignment

Conditional (If-Else)

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