JavaScript Booleans
What is a Boolean?
In JavaScript, a Boolean represents one of two values:
- true
- false
Booleans are mainly used to make decisions in code — like controlling if something happens or not.
Creating Booleans
1. Boolean Literals
let isJavaScriptFun = true;
let isSkyGreen = false;
2. Using the Boolean() Function
let x = Boolean(10); // true
let y = Boolean(0); // false
let z = Boolean(""); // false
let a = Boolean("Hello"); // true
The Boolean() function converts any value to true or false.
Examples and Outputs
Example 1: Simple Booleans
let isAdult = true;
let isChild = false;
console.log(isAdult); // Output: true
console.log(isChild); // Output: false
Example 2: Boolean Conversion
console.log(Boolean(100)); // Output: true
console.log(Boolean(0)); // Output: false
console.log(Boolean("Hi")); // Output: true
console.log(Boolean("")); // Output: false
console.log(Boolean(undefined)); // Output: false
console.log(Boolean(null)); // Output: false
Truthy and Falsy Values
JavaScript considers some values automatically as true (truthy) and others as false (falsy).
Falsy Values | Means |
---|---|
false | |
false | false |
0 | false |
-0 | false |
"" (Empty string) | false |
null | false |
undefined | false |
NaN | false |
Everything else is considered truthy (means true).
Boolean in Conditional Statements
Booleans are very important in if, while, and other conditions.
Example:
let isLoggedIn = true;
if (isLoggedIn) {
console.log("Welcome back!");
} else {
console.log("Please log in.
");
}
// Output: Welcome back!
Comparison Operations (Return Boolean)
Operators like == , === , >, <, etc., return a boolean.
Example:
console.log(10 > 5); // Output: true
console.log(3 ===
"3"); // Output: false
console.log(3 ==
"3"); // Output: true (because == does type
conversion)
Logical Operators with Booleans
Operator Description Example Output
Logical Operators with Booleans
Operator | Description | Example | Output |
---|---|---|---|
&& (AND) | Both must be true | true && false | false |
` | ` (OR) | At least one true | |
! (NOT) | Reverses boolean | !true | false |
Example:
console.log(true && false); // Output: false
console.log(true || false); // Output: true
console.log(!true);