Operators

Operators

What it means

Operators combine or compare values. JavaScript groups them into arithmetic (+, -, *, /, %, **), comparison (==, ===, <, >=, etc.), logical (&&, ||, !), and a handful of newer, more precise operators like ?? (nullish coalescing) and ?. (optional chaining).

Examples

console.log(10 % 3);        // 1 -- remainder
console.log(2 ** 8);        // 256 -- exponentiation

console.log(5 == "5");      // true  -- loose equality, coerces types
console.log(5 === "5");     // false -- strict equality, no coercion

console.log(true && "yes"); // "yes" -- && returns the last truthy operand
console.log(false || "default");   // "default"

const port = process.env.PORT ?? 3000;   // only falls back for null/undefined
const city = user?.address?.city;         // safely reads nested, possibly-missing props

Common mistake

Using == (loose equality) instead of === (strict equality) — == performs type coercion before comparing, producing surprising results for edge cases.

console.log(0 == "");        // true  -- both coerce to falsy
console.log(0 == "0");       // true
console.log("" == "0");      // false -- inconsistent, hard to predict
console.log(null == undefined);   // true

// Strict equality avoids all of this coercion
console.log(0 === "");       // false
console.log(0 === "0");      // false

Quick practice

1. What’s the key difference between == and ===?

   Answer

   == coerces operands to the same type before comparing; === compares both value and type with no coercion. === is almost always the safer choice.

2. What does ?? do differently from ||?

   Answer

   ?? only falls back on null or undefined; || falls back on any falsy value, including 0, "", and false, which is often not what you want.

3. What does user?.address?.city return if user.address is undefined?

   Answer

   undefined — optional chaining short-circuits and returns undefined instead of throwing a TypeError when it hits a null/undefined link in the chain.