Ternary Operator in JS: Everything you need to know

Nureddin Farzaliyev — Tue, 19 Nov 2024 15:39:34 +0000

What is Ternary?

Ternary Operator is a javascript operator which is available across browsers since July 2015. It is a shorthand alternative for if/else statements. This operator is widely-used in different programming languages like Java, C, Python but our focus in this article will be on javascript.

Let's check out the general syntax of ternary operator.

condition ? ifTrue : ifFalse

As you can see from the example above, ternary operator replaces if and else statements, accordingly, with ? and : symbols. The condition which is on the left-hand side of the question mark will be checked. If it is true, first expression which is between the ? and the : mark will be executed. If it's false, last expression which is written after the : symbol will be executed.

How it works?

In order to understand how ternary operator works, let's compare it with the regular if/else statement.
The Javascript code below, will log a string to the console, conditionally.

let a = 10

if(a == 10){
    console.log("Variable is ten!")
}else{
    console.log("Variable is not ten!")
}

Now, let's re-write this code using ternary operator.

let a = 10
a == 10 ? console.log("Variable is ten!") : console.log("Variable is not ten!")

Ternary operator in this code block conditionally logs the string as the way we intend. But there is a better way to write this statement.
Ternary operator not only executes the expression but also returns the value. Thus, instead of using operator to handle two different console.log expressions, we can write the statement in a way that it handles two different values which is in the one console.log statement.
For example:

let a = 10
console.log(a == 10 ? "Variable is ten!" : "Variable is not ten!")

The output of this line will be exactly same as the other ternary expression we've write before. But this code is more compact and easy-to-read.

We can use ternary operator to assign values to variables conditionally. Let's check out an example with regular if/else statements, then write it again using ternary.

let a = 10
let b
if(a === 10){
    b = a * 5
}else{
    b = a * 2
}

If a is 10, the code block will multiply it by 5, else it will multiply the variable with 2 and in both cases, will assign it to b.
The alternative using ternary operator will be just like following:

let a = 10
let b = a === 10 ? a * 5 : a * 2

As you can see it is more convenient to write a single line code for basic operations like this.

Nested Conditions

Sometimes we have to use more than one if/else conditions within each other. Ternary operator can be utilized to chain conditions.

let a = 5
if(a === 1){
    console.log("1")
}else if(a === 2){
    console.log("2")
}else{
    console.log("a is not 1 or 2")
}

This chaining of condition which is shown above can be represented using ternary operator in the following way:

let a = 5
console.log(a === 1 ? "1" : a === 2 ? "2" : "a is not 1 or 2")

As you can predict, this can get very messy easily. That's why using ternary operator in complex conditional statements is not required.

Ternary in React

If you have build a React application before, you probably know that conditional rendering is an important topic. Ternary operator makes this operation easier. Let's check out an example from the official page of React.
This is the regular way of writing the statement:

if (isPacked) {
  return <li className="item">{name} ✅</li>;
}
return <li className="item">{name}</li>;

And this is the same statement, but using ternary operator.

return (
  <li className="item">
    {isPacked ? name + ' ✅' : name}
  </li>
);

As you can see it looks much more better. Thus, sometimes it is cleaner and better approach to write statements with ternary, especially while working with React. But in some cases, ternary operator can make code even harder to read.

In which other situations, do you think, we have to use or avoid ternary operator? Please let me know your thoughts in comments!

Thank you for reading.
Please check out these links for further reading.

More about Ternary Operator: Conditional (ternary) operator - MDN Web Docs
More about Conditional Rendering in React: Conditional Rendering - React

DEV Community: Nureddin Farzaliyev

Ternary Operator in JS: Everything you need to know

What is Ternary?

How it works?

Nested Conditions

Ternary in React