Javascript’s Ternary Operator: A Compact Alternative to if/else

Javascript offers a ternary operator which acts like a one-line if/else statement with a single condition. It works really well for conditionally assigning a value to a variable.

For Assigning a Value to a Variable

Here’s what assigning a value to a variable conditionally using a ternary looks like. For the purposes of this example, imagine itemCost is the cost of the current item and hasDiscount has been set to true or false depending on whether this user gets a discount.

const markup = 0.3;
const baseItemPrice = itemCost * (1 + markup);
const itemPrice = hasDiscount ? baseItemPrice * 0.8 : baseItemPrice;

The part before the question mark is the condition. The next part is the code to be executed if the condition evaluates to true. After the colon, we have the code to run if the condition is false.

It would look like this if you wrote it as an if statement:

const markup = 0.3;
const baseItemPrice = itemCost * (1 + markup);
if (hasDiscount) {
 const itemPrice = baseItemPrice * 0.8;
} else {
 const itemPrice = baseItemPrice;
}

Here’s what the ternary example above does in plain English. We create two variables: markup which is how much we mark up our items and baseItemPrice which is the price we charge after applying our markup. We assign a value to itemPrice using a ternary. The ternary checks to see if the customer has a discount. If they do, it sets the final itemPrice to 80% of the base price. If not, itemPrice is set to baseItemPrice.

For Other Operations

Imagine a user just submitted a form. You know the user is either from the US or the UK. You also know the user typed the word “color” as part of one of the fields. You’re going to use that to determine which country they are from and run a function to add them to an email list based on their location.

For the purposes of this example, we’ll assume the form responses have already been serialized to an object called responses.

responses.colorField.includes('colour') ? addToUKList(responses.email) : addToUSList(responses.email);

When to Use the Ternary

The ternary is a cool trick, but you shouldn’t use it all the time. It’s extremely important that your code is readable, and the ternary just doesn’t read as nicely as the humble if statement.

I use them mostly for assignment, particularly when I have a series of conditional assignments in close proximity, just to make the code a little more compact. When I need to conditionally do something besides assignment, I’ll almost always reach for a different method.

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If you think the ternary will be useful, why not add the array reduce method to your toolkit as well!

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