What are truthy values in JavaScript?

Truthy values evaluate to true when coerced by JavaScript’s typing engine into a boolean value. Most values are truthy in JavaScript, including the empty array [] and the empty object {}.

Truthy values in JavaScript

“A truthy value simply means a value that is considered true when evaluated in a boolean context” — Mozilla Developer Network

Any primitive type will evaluate to true in JavaScript, with the exception of the following 7 values, which are called falsy values:

• the number 0
• the BigInt 0n
• the keyword null
• the keyword undefined
• the boolean false
• the number NaN
• the empty string “” (equivalent to `` or ‘’)

Values not on the list of falsy values in JavaScript are called truthy values and include the empty array [] or the empty object {}.

This means almost everything evaluates to true in JavaScript — any object and almost all primitive values, everything but the falsy values.

Specifically, they evaluate to true when given a boolean context, such as an if statement or the question mark e>? operator.

Code example of truthy values

The truthy values are called truthy because they evaluate to true, and the falsy values are called falsy because they evaluate to false:

Conclusion

“Truthiness (noun) — the belief in what you feel to be true rather than what the facts will support” Stephen Colbert

In programming JavaScript, it can be really useful to write a conditional statement to check if a value is set or not.

While it doesn’t work quite right for objects including arrays, primitive types in JavaScript have certain falsy values to mean empty or zero.

Everything else in JavaScript is a truthy value and evaluates to true.

So, trust your gut: your value is going to evaluate to true. 🤨

Further reading

• The Sitepoint library has an article about truth & falsy in JavaScript:

• Brandon Morelli explains that while truthy values evaluate to true in a boolean context, they do not loosely equal (==) the boolean value true in an in-depth article over at codeburst.io:

• Lokesh Gupta wrote about truthy in JavaScript at HowToDoInJava:

• Wojciech Trawiński explains why truthy matters in JavaScript everyday:

Dr. Derek Austin is the author of Career Programming: How You Can Become a Successful 6-Figure Programmer in 6 Months, now available on Amazon.