The `typeof` Operator in JavaScript

The `typeof` Operator in JavaScript

The `typeof` Operator in JavaScript

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

The typeof operator returns the type of a given variable as a string.

typeof 42; // 'number'
typeof 'test'; // 'string'
typeof true; // 'boolean'
typeof (void 0); // 'undefined'
typeof BigInt('1234'); // 'bigint'
typeof Symbol('foo'); // 'symbol'
typeof ({ answer: 42 }); // 'object'
typeof function() {}; // 'function'

// As far as 'typeof' is concerned, all objects are the same.
class MyClass {}
typeof (new MyClass()); // 'object'

Here’s the general idea: the typeof operator returns which of the 8 JavaScript data types a given value is. There’s one key exception to this rule: null.

With null

The one big gotcha with typeof is that typeof null === 'object'. There is a historical reason for this behavior, and a proposal to change this behavior was rejected, so it looks like JavaScript is stuck with this quirk.

The workaround to check whether a value is actually an object with typeof is to check whether the type is 'object' and the value
is not strictly equal to null.

function isObject(v) {
  return typeof v === 'object' && v !== null;

Error Cases

The typeof operator can throw an error if you use it on a block scope variable before you define it.

// Throws 'ReferenceError: v is not defined'
console.log(typeof v);

let v;

This behavior only applies for block scoped variables. For example, if you don’t define v at all, the above script will work fine.

console.log(typeof v); // 'undefined'

//let v;

Block scoped variables are the only case where typeof throws an error. Otherwise, typeof will always succeed.

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More Fundamentals Tutorials

  • 3 Patterns to Merge Arrays in JavaScript
  • Convert a BigInt to a Number in JavaScript
  • The parseInt Function in JavaScript
  • The toFixed() Function in JavaScript
  • The Nullish Coalescing Operator ?? in JavaScript
  • Implementing Tuples in JavaScript
  • Convert a JavaScript Enum to a String

JavaScript Fundamentals for  The `typeof` 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.
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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.
  • 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.
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I hope this helps for The `typeof` Operator in JavaScript !

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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