What does the ? question mark mean in JavaScript code?

What does the ? question mark mean in JavaScript code?

The question mark ? is an alternative to an if statement best used in the case where one of two values will be assigned to a variable based on a conditional statement.

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The purpose of the question mark operator ? is to return one value or another depending on its condition. ? JavaScript.info in August 2019

?A ?? ?What is a ? doing in my JavaScript code?? The ? character jumped off the screen when it showed up in my JavaScript programming.

Thankfully, the question mark (or question mark ? colon) syntax is easy to understand, but overusing the ? : can make code hard to read.

The question mark is used in JavaScript as an alternative to an if statement, especially in the case where a value is assigned based on a conditional.

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A question mark by another name

[The] ?question mark? or ?conditional? operator in JavaScript is a ternary operator that has three operands. ? GeeksForGeeks

It has many names: question mark, question ? colon, ternary operator. While the syntax is pretty straight forward, describing the JavaScript question mark ? aloud can be difficult due to its terminology.

The question mark operator ? takes three operands: some condition, a value if that condition is true, and a value if that condition is false.

It is used in JavaScript to shorten an if else statement to one line of code.

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Three of a kind ? the ternary opreator

The conditional (ternary) operator is the only JavaScript operator that takes three operands. This operator is frequently used as a shortcut for the if statement. ? MDN Web Docs

As an operator taking three operands, the question mark is also called the ternary operator ? with ternary meaning composed of three parts:

  1. The condition lives in parentheses
  2. The value if true comes first
  3. The value if false comes second

The three operands look like this: (1+1==2) ? “Pass” : “Fail”. The question mark and colon operators together are the ternary operator.

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Take a look at my ?

Question marks are useful in JavaScript for quickly assigning a different value to a variable based on a condition, a very common task.

The determination of the bonus only takes one line, so I am able to use the save time that I would have spent writing if, else, and {} blocks.

Technically the parentheses are optional, but they improve readability:

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Watch out for ?

Most developers think this code is hard to read, even though the question mark operator let me write it in just a single line of code:

Compare this to the alternative, written with an if statement:

The typical best practice is to reserve the question mark for cases of assigning variables, when it makes sense to use the question ? colon in JavaScript.

In other cases, where I am taking some action if something is true, then I try to stick with if statements so as to make my code clearer.

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Additional resources

  • Tania Rascia explains conditional statements on DigitalOcean:

If Statements, If Else Statements, Nested If, Ternary Operators | DigitalOcean

In programming, there will be many occasions in which you will want different blocks of code to run depending on user?


  • Stephen Chapman explains what he likes about the ? on ThoughtCo:

An Effective Shortcut Using the ‘Ternary’ Operator in JavaScript

The conditional ternary operator in JavaScript assigns a value to a variable based on some condition and is the only?


  • Brandon Morelli likes how terse the ternary operator is on codeburst.io:

JavaScript ? The Conditional (Ternary) Operator Explained

Shorten your if statements into one line of code with the conditional operator



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