conditional operator in javascript

How do you use the ? : (conditional) operator in JavaScript?

stackoverflow.com › questions › 6259982 › how-do-you-use-the-conditional-operator-in-javascript

This is a one-line shorthand for an if-else statement. It's called the conditional operator.¹

Here is an example of code that could be shortened with the conditional operator:

var userType;
if (userIsYoungerThan18) {
  userType = "Minor";
} else {
  userType = "Adult";
}

if (userIsYoungerThan21) {
  serveDrink("Grape Juice");
} else {
  serveDrink("Wine");
}

This can be shortened with the ?: like so:

var userType = userIsYoungerThan18 ? "Minor" : "Adult";

serveDrink(userIsYoungerThan21 ? "Grape Juice" : "Wine");

Like all expressions, the conditional operator can also be used as a standalone statement with side-effects, though this is unusual outside of minification:

userIsYoungerThan21 ? serveGrapeJuice() : serveWine();

They can even be chained:

serveDrink(userIsYoungerThan4 ? 'Milk' : userIsYoungerThan21 ? 'Grape Juice' : 'Wine');

Be careful, though, or you will end up with convoluted code like this:

var k = a ? (b ? (c ? d : e) : (d ? e : f)) : f ? (g ? h : i) : j;

¹ Often called "the ternary operator," but in fact it's just a ternary operator [an operator accepting three operands]. It's the only one JavaScript currently has, though.

Answer from Peter Olson on Stack Overflow

MDN Web Docs

developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › Conditional_operator

Conditional (ternary) operator - JavaScript | MDN

The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark (?), then an expression to execute if the condition is truthy followed by a colon (:), and finally the expression to execute if the condition is falsy.

Stack Overflow

stackoverflow.com › questions › 6259982 › how-do-you-use-the-conditional-operator-in-javascript

How do you use the ? : (conditional) operator in JavaScript? - Stack Overflow

Top answer

1 of 16

771

This is a one-line shorthand for an if-else statement. It's called the conditional operator.¹

Here is an example of code that could be shortened with the conditional operator:

var userType;
if (userIsYoungerThan18) {
  userType = "Minor";
} else {
  userType = "Adult";
}

if (userIsYoungerThan21) {
  serveDrink("Grape Juice");
} else {
  serveDrink("Wine");
}

This can be shortened with the ?: like so:

var userType = userIsYoungerThan18 ? "Minor" : "Adult";

serveDrink(userIsYoungerThan21 ? "Grape Juice" : "Wine");

Like all expressions, the conditional operator can also be used as a standalone statement with side-effects, though this is unusual outside of minification:

userIsYoungerThan21 ? serveGrapeJuice() : serveWine();

They can even be chained:

serveDrink(userIsYoungerThan4 ? 'Milk' : userIsYoungerThan21 ? 'Grape Juice' : 'Wine');

Be careful, though, or you will end up with convoluted code like this:

var k = a ? (b ? (c ? d : e) : (d ? e : f)) : f ? (g ? h : i) : j;

¹ Often called "the ternary operator," but in fact it's just a ternary operator [an operator accepting three operands]. It's the only one JavaScript currently has, though.

2 of 16

183

I want to add some to the given answers.

In case you encounter (or want to use) a ternary in a situation like 'display a variable if it's set, else...', you can make it even shorter, without a ternary.

Instead of:

var welcomeMessage  = 'Hello ' + (username ? username : 'guest');

You can use:

var welcomeMessage  = 'Hello ' + (username || 'guest');

This is Javascripts equivallent of PHP's shorthand ternary operator ?:

Or even:

var welcomeMessage  = 'Hello ' + (username || something || maybethis || 'guest');

It evaluates the variable, and if it's false or unset, it goes on to the next.

Discussions

Im trying to understand the "Conditional (ternary) operator." Do these 2 codes mean the same thing? I wrote the if statement

Yeah, but please do not code like that. Keep Ternary statements simple, otherwise use something else (if or switch) More on reddit.com

r/learnjavascript

187

July 14, 2021

[AskJS] Nullish Check in conditional

value == null only matches null and undefined, not any other falsy values. This is the only time you should use == over ===. More on reddit.com

r/javascript

August 16, 2024

Conditionally spreading objects in JavaScript

2.4M subscribers in the javascript community. Chat about javascript and javascript related projects. Yes, typescript counts. Please keep self promotion to a minimum/reasonable level. More on reddit.com

r/javascript

152

September 19, 2022

how to wrap a map return in a div using conditional rendering w ternary operator in react?

You could just change the className depending on history.length and probably use a wrapper . Or maybe like this {history.length ? ( {history .slice(Math.max(history.length - 10, 0)) .map((entry, index) => { return

{entry}

; }) } ) : ( Go do! )} More on reddit.com

r/reactjs

December 23, 2023

How do you use the ? : (conditional) operator in JavaScript?

stackoverflow.com › questions › 6259982 › how-do-you-use-the-conditional-operator-in-javascript

This is a one-line shorthand for an if-else statement. It's called the conditional operator.¹

Here is an example of code that could be shortened with the conditional operator:

var userType;
if (userIsYoungerThan18) {
  userType = "Minor";
} else {
  userType = "Adult";
}

if (userIsYoungerThan21) {
  serveDrink("Grape Juice");
} else {
  serveDrink("Wine");
}

This can be shortened with the ?: like so:

var userType = userIsYoungerThan18 ? "Minor" : "Adult";

serveDrink(userIsYoungerThan21 ? "Grape Juice" : "Wine");

Like all expressions, the conditional operator can also be used as a standalone statement with side-effects, though this is unusual outside of minification:

userIsYoungerThan21 ? serveGrapeJuice() : serveWine();

They can even be chained:

serveDrink(userIsYoungerThan4 ? 'Milk' : userIsYoungerThan21 ? 'Grape Juice' : 'Wine');

Be careful, though, or you will end up with convoluted code like this:

var k = a ? (b ? (c ? d : e) : (d ? e : f)) : f ? (g ? h : i) : j;

¹ Often called "the ternary operator," but in fact it's just a ternary operator [an operator accepting three operands]. It's the only one JavaScript currently has, though.

Answer from Peter Olson on Stack Overflow

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