Truthy and Falsy Values

Part of the Fundamentals section of Coddy's Lua journey — lesson 24 of 90.

When using logical operators like and, or, and not, Lua needs to determine what counts as "true" or "false" in logical contexts. This concept is called truthy and falsy values, and Lua handles it differently from many other programming languages.

In Lua, only two values are considered falsy (treated as false in logical operations):

print(false and "This won't print")  -- false is falsy
print(nil and "This won't print")    -- nil is falsy

Everything else in Lua is considered truthy (treated as true in logical operations). This includes values that might surprise you if you're coming from other languages:

print(0 and "This will print")      -- 0 is truthy in Lua!
print("" and "This will print")     -- Empty string is truthy!
print({} and "This will print")     -- Empty table is truthy!

Cheat sheet

In Lua, only two values are considered falsy (treated as false in logical operations):

false
nil

Everything else is truthy, including:

0 (unlike many other languages)
Empty strings ""
Empty tables {}

print(false and "Won't print")  -- false is falsy
print(nil and "Won't print")    -- nil is falsy
print(0 and "Will print")       -- 0 is truthy in Lua
print("" and "Will print")      -- Empty string is truthy

Try it yourself

This lesson doesn't include a code challenge.