Programming Fundamentals › Programming Basics

Ternary Operator

A compact inline if/else expression.

Also known as: conditional operator, inline if, ternary expression

The ternary operator is a compact inline if/else that produces a value. It takes three parts: a condition, a result if true, and a result if false.

const label = age >= 18 ? "adult" : "minor";

label = "adult" if age >= 18 else "minor"

Because it’s an expression, you can use it anywhere a value goes: assignments, arguments, template strings, JSX.

<p>{items.length ? `${items.length} items` : "Empty"}</p>

When it helps

Choosing between two simple values, with no side effects.

When it hurts

Nesting makes it unreadable:

const x = a ? b ? 1 : 2 : c ? 3 : 4;      // don't

Use if/else, an early return or a lookup table when there are more than two outcomes, or when the branches do actions rather than produce values (conditionals, switch).

Gotchas

• Both branches should return compatible types, or the result type becomes a union.
• It evaluates only the chosen branch, so it’s safe for guards (user ? user.name : "guest").
• For a default when a value is missing, ?? (JavaScript) or or (Python) is shorter, but mind the truthy rules.
• Python’s order is unusual: value-if-true comes first, then the condition.

Rule of thumb: if you have to read it twice, write it as an if.