Double question mark in JavaScript

Double question mark Javascript [Explained]

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Have you heard of the Double Question Mark operator in JavaScript? It’s a powerful tool that many people aren’t familiar with.

In this article, we’ll dive into what it does and how it can make your JavaScript code even better.

Get ready to level up your skills!

What is the Double Question Mark (??) operator?

The double question mark (??) also known as “nullish coalescing operator,” made its debut in ECMAScript 2020.

It offers a sleek and efficient solution for managing default values in situations involving nullable or undefined variables.

With this operator, you can elegantly handle such scenarios without compromising code readability.

Differences between the Double Question Mark operator and the Logical OR (||) operator

While the Double Question Mark operator and the Logical OR (||) operator may appear similar, they exhibit distinct behaviors when encountering specific values.

The Logical OR operator returns the right-hand side value if the left-hand side value is considered falsy, encompassing null, undefined, 0, and an empty string.

On the other hand, the Double Question Mark operator solely yields the right-hand side value if the left-hand side value is strictly null or undefined, differentiating it from other false values.

Syntax and Examples

The syntax of the Double Question Mark operator is straightforward.It can be used as follows:

const result = valueToCheck ?? defaultValue;

Here’s an example that demonstrates the basic usage of the Double Question Mark operator:

const sampleNum = null;
const fallbackValue = 17;
const value = sampleNum ?? fallbackValue;
console.log(value);

Output:

17

In this case, the Double Question Mark operator checks if sampleNum is null or undefined and assigns the value of fallbackValue to value if that’s the case.

The Double Question Mark operator can also be chained together for more complex scenarios:

const itscUser = {
  name: 'It Sourcecode',
  address: null,
};

const itscCountry = itscUser.address?.itscCountry ?? 'Unknown';
console.log(itscCountry);

Output:

Unknown

In this example, the optional chaining operator (?.) is used in conjunction with the Double Question Mark operator. It also safely accesses the itscCountry property within the address object, even if address itself is null or undefined.

Use Cases for the Double Question Mark Operator

The Double Question Mark operator offers versatile applications that can significantly improve the reliability and clarity of our JavaScript code in different situations.

Here are some common use cases:

Defaulting variable values

let username = null;
let defaultItscName = '@Itsourcecode';

const displayUserName = username ?? defaultItscName;
console.log(displayUserName);

Output:

@Itsourcecode

In the example above, the Double Question Mark operator allows us to set a default value for the username variable if it is null or undefined.

This ensures that our code doesn’t break or behave unexpectedly when the variable is not explicitly defined.

Safely accessing nested properties

const website = {
  SiteName: 'itsourcecode',
  address: {
    city: 'Manila',
    country: null,
  },
};

const itscCountry = website.address.country ?? 'Unknown';
console.log(itscCountry);

Output:

Unknown

When dealing with nested objects or properties, the Double Question Mark operator helps us avoid errors caused by accessing properties that might be null or undefined.

It allows us to gracefully handle such cases and provide a fallback value when necessary.

Checking for null or undefined values

const value = null;
const itscResult = value ?? '@itsourcecode';
console.log(itscResult);

Output:

@itsourcecode

By using the Double Question Mark operator, we can easily check for null or undefined values and provide a fallback value.

This is especially handy when dealing with user inputs, API responses, or situations where we need to handle null or undefined values.

Browser Compatibility and Polyfills

The Double Question Mark operator is a relatively new addition to JavaScript, and its support might vary across different browsers and environments.

Before using it in production code, it is essential to consider the targeted browser versions and verify their compatibility.

In scenarios where support is lacking, polyfills or alternative approaches can be used to achieve similar functionality.

Benefits of Using the Double Question Mark Operator

Improved code readability

The Double Question Mark operator provides a concise and expressive way to handle null or undefined values, making the code more readable and easier to understand.

By using this operator, the intent of the code becomes clear, and potential pitfalls related to null or undefined values can be avoided.

Reduced potential for bugs

Handling null or undefined values can be error-prone, leading to unexpected behavior or crashes.

By using the Double Question Mark operator, we can reduce the chances of encountering such bugs and improve the overall reliability of our JavaScript code.

Anyway here are some of the functions you might want to learn and can help you:

Conclusion

In conclusion, Double Question Mark in Javascript operator is a valuable addition to JavaScript, providing a convenient way to handle null or undefined values and set default values when necessary.

By leveraging its power, we can write more robust and readable code that gracefully handles various scenarios.

That concludes our discussion on this function. We hope that you have gained valuable insights from this article.

Stay tuned for more! 😊

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