How to use booleans and comparisons

Create boolean values

A boolean is exactly true or false. Comparisons produce booleans.

const isMember = true;
const temperature = 24;
const isWarm = temperature >= 20;
console.log(isMember, isWarm);

Use strict equality

Prefer === and !==; they compare without converting operands first.

console.log(5 === 5);   // true
console.log("5" === 5); // false
console.log("5" == 5);  // true: coercion, usually avoid

Combine conditions

&& means both, || means either, and ! negates a value. Parentheses clarify mixed expressions.

const age = 20;
const hasTicket = true;
const canEnter = age >= 18 && hasTicket;
console.log(canEnter);
console.log(!canEnter);

Understand truthy and falsy

• false, 0, "", null, undefined, and NaN are falsy
• Most other values, including empty arrays and objects, are truthy
• Use explicit comparisons when zero or an empty string is valid data
• Logical operators short-circuit and return operands, not necessarily booleans