Ternary

Learn to write a conditional expression in one line with ? :.

The ternary operator

To pick one of two values in a single line you use the ternary operator ? :. The form is condition ? valueA : valueB. If the condition is true, valueA; otherwise valueB is returned.

For example const msg = age >= 18 ? "Adult" : "Child"; makes an assignment in one line. The same logic could be written with if/else, but ternary is shorter. It is especially useful when assigning to a variable or using inside an expression; for complex logic if/else reads better.

Nested ternary

To select among three or more values you can nest ternary: cond1 ? valueA : cond2 ? valueB : valueC. If the first condition is true, valueA; otherwise the second condition is tested.

For example const grade = score >= 90 ? "A" : score >= 80 ? "B" : "C"; picks one of three grades in one line. Nested ternary is compact but reduces readability when overused. For more than three branches an if/else if chain is usually better; nested ternary is preferred only for simple assignments.

Exercise Adult check

The age variable is set to 20. Declare a variable msg and assign the ternary age >= 18 ? "Adult" : "Child" to it. Then print msg with console.log. The output on a single line must be Adult.

Show example solution

const age = 20;
const msg = age >= 18 ? "Adult" : "Child";
console.log(msg);

Test yourself

What is the result of 5 > 3 ? "a" : "b"?
```
5 > 3 ? "a" : "b"
```
- true
- "b"
- "a"
- 5
Show answer

"a" — The condition 5 > 3 is true; the ternary returns "a".
Match each part to its meaning

condition ?

Tests the condition
between ? and :

True value
after :

False value
const x =

Assignment target

Write the ternary expression

const age = 20;
const msg = age >= 18 ? "Adult" ____ "Child";

Show answer

const age = 20;
const msg = age >= 18 ? "Adult" : "Child";

Next lesson: Optional chaining

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