Nullish Coalescing Operator ?? in JavaScript

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2 years ago

Nullish Coalescing Operator ?? in JavaScript

In this post, we will give you information about The Nullish Coalescing Operator ?? in JavaScript. Here we will give you detail about The Nullish Coalescing Operator ?? in JavaScript And how to use it also give you a demo for it if it is necessary.

The nullish coalescing operator provides a concise syntax for setting a default value if the given value is nullish.
null and undefined are the only nullish values in JavaScript.

function getAnswer(answer) {
  // Return '42' if 'answer' is null or undefined, otherwise return 'answer'
  return answer ?? 42;
}

getAnswer('hello'); // 'hello'
getAnswer(''); // ''
getAnswer(0); // 0

getAnswer(null); // 42
getAnswer(undefined); // 42

Nullish coalescing is typically used for assigning default values.
Older JavaScript code often used || for assigning default values, but || is error prone because it captures all falsy values, like , empty string, and false.

function format(options) {
  // Good: 'uppercase' will be 'true' if 'options' is not specified,
  // or if 'options.uppercase' is 'null' or 'undefined'.
  const uppercase = options?.uppercase ?? true;

  // Bad! 'uppercase' will be 'true' if 'options.uppercase === false'
  const uppercase = options?.uppercase || true;
}

Nullish Coalescing Assignment for Nullish Coalescing Operator ?? in JavaScript

The nullish coalescing assignment operator is similar to the nullish coalescing operator, just for assignments. Nullish coalescing assignment only assigns the value if the left hand side is nullish.
x ??= y is equivalent to x = x ?? y.

function setDefaultOptions(options) {
  // If 'options.uppercase' is 'null' or 'undefined', set to 'true'.
  // Otherwise, no-op
  options.uppercase ??= true;

  // The following is equivalent
  options.uppercase = options.uppercase ?? true;
}

Pre-ES2020 Alternative for Nullish Coalescing Operator ?? in JavaScript

The nullish coalescing operator was introduced in ES2020, which makes it a relatively new addition to the JavaScript language.
For example, the nullish coalescing operator isn’t supported in Node.js 12.
However, there is a concise alternative with the ternary operator that works in any version of JavaScript.

function getAnswer(answer) {
  // Equivalent to 'return answer ?? 42;'
  return answer == null ? 42 : answer;
}

JavaScript Fundamentals for Nullish Coalescing Operator ?? in JavaScript

JavaScript is a programming language that is used to create interactive web pages. It is a client-side scripting language, which means that it runs on the user’s browser. JavaScript can be used to add animation, interactivity, and functionality to web pages.

Here are some of the fundamentals of JavaScript:

Variables: Variables are used to store data. They are declared using the var keyword.
Data types: JavaScript has a variety of data types, including strings, numbers, booleans, objects, and arrays.
Operators: Operators are used to perform operations on data.
Control flow statements: Control flow statements allow you to control the order in which your code is executed.
Functions: Functions are blocks of code that can be reused.
Objects: Objects are used to store data in key-value pairs.
Arrays: Arrays are used to store data in a sequential order.
Events and event handlers: Events are notifications that are sent by the browser when something happens, such as when the user clicks on an element or moves the mouse over an element. Event handlers are functions that are called in response to an event.
DOM manipulation: The Document Object Model (DOM) is a tree-like structure that represents the elements of a web page. JavaScript can be used to manipulate the DOM to change the appearance or behavior of a web page.

These are just some of the fundamentals of JavaScript. There are many other concepts that you can learn as you continue to develop your skills.

Here are some resources that you can use to learn more about JavaScript:

Mozilla Developer Network (MDN): The MDN is a great resource for learning about JavaScript. It has a comprehensive reference guide, tutorials, and articles on a wide range of topics.
W3Schools: W3Schools is another great resource for learning about JavaScript. It has interactive tutorials and quizzes that can help you learn the basics of the language.
JavaScript.info: JavaScript.info is a website that provides in-depth tutorials on JavaScript. It also has a forum where you can ask questions and get help from other JavaScript developers.

I hope this helps!

Here are some additional tips for learning JavaScript:

Start with the basics: Before you start trying to build complex applications, it’s important to learn the basics of JavaScript. This includes things like variables, data types, operators, and control flow statements.
Practice regularly: The best way to learn JavaScript is to practice regularly. Try to find some time each day to work on JavaScript projects.
Get help from others: If you get stuck, don’t be afraid to ask for help from others. There are many online forums and communities where you can get help from other JavaScript developers.

With a little practice, you’ll be able to learn JavaScript and start building amazing web applications.

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