JavaScript Booleans & Comparisons

Definition: A boolean is either true or false. Comparisons produce booleans, and booleans drive every decision in your code.

Example 1 — comparison operators

console.log(10 > 9);    // true
console.log(10 < 9);    // false
console.log(10 >= 10);  // true
console.log(5 === 5);   // true (value AND type)
console.log(5 !== 3);   // true

Example 2 — === vs ==

Prefer strict ===. Loose == converts types and can confuse:

console.log(5 == "5");   // true  (loose, converts)
console.log(5 === "5");  // false (strict, safer)
console.log(0 == "");    // true  (surprising!)
console.log(0 === "");   // false (clear)

Example 3 — truthy and falsy

These values count as false: 0, "", null, undefined, NaN. Everything else is truthy:

console.log(Boolean(0));    // false
console.log(Boolean(""));   // false
console.log(Boolean("hi")); // true
console.log(Boolean(123));  // true

💡 Takeaway: sticking to === removes a whole class of beginner bugs.