Operators and conditionals

In plain English

Operators are symbols that do work on values: arithmetic operators like +, -, * and / do maths. Comparison operators like === ask a yes-or-no question and produce a boolean (true or false); the strict === checks that both the value and its type match, while the loose == converts types first, which is why "5" == 5 is true but "5" === 5 is false. Logical operators combine conditions, where && means AND, || means OR and ! means NOT. An if/else statement runs one block of code when a condition is true and another when it is false, and a ternary (? :) is a short way to pick between two values.

Step by step

1. 1Write an expression using arithmetic operators and log the result.
2. 2Compare two values with === and check the boolean it returns.
3. 3Combine conditions with &&, || and !.
4. 4Branch with if/else, then rewrite the same choice as a ternary.
5. 5Test which values JavaScript treats as falsy.

const price = 20;
const taxRate = 0.1;

const total = price + price * taxRate;

const isBigSpender = total >= 25;
const isMember = true;

if (isBigSpender && isMember) {
  console.log("10% member discount applied");
} else {
  console.log("No extra discount");
}

const emptyName = "";
const fallback = emptyName || "Guest";

const label = total > 25 ? "Big total" : "Budget total";
console.log(label, fallback);

Common mistakes

• Using a single = when you meant to compare, because = assigns a value and does not check equality.
• Relying on == and being surprised when "5" == 5 comes out true.
• Forgetting that 0, "", null, undefined and NaN are all falsy values.
• Writing a hard-to-read ternary when a plain if/else would be clearer.