Feb 8, 2019

JS Basics: Ternary Operator

A ternary or conditional operator is like an inline if statement. In JavaScript, you can identify them by their unique use of a question mark, ?, and colon, :.

When I first started coding, I found ternary operators more than a little confusing, so let’s try to unpack them. Look at this common example:

<span
className={`Todo ${props.isDone ? 'Todo--done' : ''}`}
>
{props.text}
</span>

Here we have a snippet from a React to-do app with a ternary operator. The class ( className in JSX) is being set based on a condition in our props object. Here’s how to read a ternary operator:

If props.isDone is true/truthy, then return the string “Todo–done”; otherwise return an empty string.

Written out, a ternary operator looks like an if statement. We could express the same code like this:

if (props.isDone === true) {
return 'Todo--done'
} else {
return ''
}

That looks more familiar! Ternary operators are useful because they allow you to add inline conditions to your code. Compare the original code to our final if statement. The ternary operator is shorter, cleaner, and more efficient.

MDN has a great list of other examples for you to reference. You can check them out here: Conditional (ternary) operators

Happy coding!

An illustration of Sean McPherson's face

My name is Sean McPherson, and I'm a software developer and educator living in Atlanta, GA.

I write about React, JavaScript, accessibility, user experience, and occassionally some other topics.