Boolean

In one line

A boolean is a value that can only be true or false — used for making decisions in code.

In simple words

A boolean is the simplest data type: it has exactly two possible values, true or false. Booleans are the foundation of conditional logic — the "if this, then that" reasoning that lets programs make decisions.

You get boolean values from comparisons (5 > 3 is true, 10 === 20 is false) and from functions that answer yes/no questions (isLoggedIn(), isValid(email)). They are also stored in flags like isReady or hasError to track on/off state.

Booleans combine with logical operators like AND (&&), OR (||), and NOT (!) to build complex conditions. For example, if (isLoggedIn && hasPermission) runs only when both are true.

Example

javascript

let isAdult = true;
let hasLicense = false;

console.log(isAdult && hasLicense);  // false
console.log(isAdult || hasLicense);  // true
console.log(!isAdult);              // false

Booleans combine with && (AND), || (OR), and ! (NOT) to build conditions.

Related terms

Related Resources

Related Lessons

Conditions
Booleans drive if/else decisions

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