if, else if, else

Braces instead of indentation

Branching is how a program makes decisions: charge shipping or not, show the data or an error. You already think in if/elif/else from Python, so this lesson is purely about the new spelling.

Python used a colon and indentation. JavaScript wraps the condition in parentheses and the body in curly braces { }. Indentation is just for humans here, the braces are what count.

const temp = 28;

if (temp >= 30) {
  console.log("Hot");
} else if (temp >= 20) {
  console.log("Warm");
} else {
  console.log("Cold");
}

The translation table from Python:

Conditions are checked top to bottom and only the first true branch runs, exactly like Python.

The conditional operator: an if/else that is a value

JavaScript also has a compact operator for choosing between two VALUES: condition ? a : b gives a when the condition is true, otherwise b. It is called the ternary operator (ternary = it takes three parts), and it exists because an if/else is a statement, not a value — you cannot drop one into the middle of a template literal or a return. The ternary can go anywhere a value goes:

const age = 20;
const label = age >= 18 ? "adult" : "minor";
console.log(`Status: ${label}`);   // Status: adult

Python spells the same idea "adult" if age >= 18 else "minor". Use the ternary for one small choice between two values; the moment you want multiple statements or nested choices, a real if/else reads better.