How do you use the ternary operator in JavaScript?

The ternary operator, also known as the conditional operator, is a shorthand way of writing an `if-else` statement in JavaScript. It has the following syntax:

condition ? expressionIfTrue : expressionIfFalse;

Here's how it works:

- If `condition` is true, the expression before the `:` (colon) is evaluated and returned.

- If `condition` is false, the expression after the `:` is evaluated and returned.

Here's an example:

let age = 20;

// Using a ternary operator to determine if a person is eligible to vote

let eligibility = age >= 18 ? "Eligible" : "Not eligible";

console.log(eligibility);  // Outputs: "Eligible"

In this example, the condition `age >= 18` is true, so the expression before the `:` ("Eligible") is evaluated and assigned to the variable `eligibility`.

You can also use the ternary operator for simple assignments or expressions within larger statements:

let isRaining = true;

// Using a ternary operator to set the value of an alert message

let alertMessage = isRaining ? "Bring an umbrella" : "Enjoy the weather";

console.log(alertMessage);  // Outputs: "Bring an umbrella"

It's important to use the ternary operator judiciously. While it's great for concise and simple conditional expressions, complex logic might be more readable with a traditional `if-else` statement.