To crack interview questions in JavaScript, you need to know some basic and important questions. These questions will help you to crack any interview or technical exams. In this article, I have mentioned the top 20 questions related to JavaScript.

1. What is the definition of JavaScript?

JavaScript is a dynamic programming language. It is used to create dynamic web pages. You can integrate HTML and CSS with JavaScript to provide a website with a real-time update. This programming language is widely used to develop PC and mobile games and applications.

*2. *Name the different data types in Javascript.

JavaScript programming language has 8 data types. They are string, number, Boolean, null, symbol, undefined, object and array.

• When some characters are arranged in a sequence, it is called a string.

• Numbers are just digits in JavaScript. These numbers can be integer and floating

• Undefined is a variable that is declared but not assigned.

• Null is a kind of sequence that is empty.

• Symbols are used to form unique keys.

• An object is a complex data type. It is a combination of entities.

• Arrays are used to hold values.

3. What is the exact definition of Hoisting?

Hoisting is an important concept in JavaScript. You can use Hoisting before declaring functions in JavaScript. You can also use it to declare variables. Hoisting is the nature of JS interpreters. You can check how I use JS hoisting in this calculator tool.

4. What is a debugger in JavaScript?

If you are a developer, a debugger is a useful tool for you to monitor and control JavaScript code easily. If an error or bug occurs, the debugger will let you know immediately. Then, you can fix and execute them.

5. What is the function of local storage and session storage in JavaScript?

If you want to store your data in a web browser, you can use local storage. This storage helps you store information. You can store up to 5 MB of data. Season storage is slightly different from it. You can store temporary data using the session storage.

6. What are Closures?

Closure is an important topic in JavaScript. You can access variables from other functions using closures. This means you are calling variables from the outer functions while staying in the inner function. This closure concept is used in data encapsulation and partial applications. You can activate modular in JavaScript.

7. How many bubbles are there in JavaScript?

There is an important concept in JavaScript. This concept is called Event bubbling. This bubbling process occurs in the DOM during event propagation. When you click an event, it executes a handler. This handler goes all along to the root of a document. This whole process is called event bubbling.

8. How many errors are there in JavaScript?

There are seven types of errors in JavaScript. They are syntax, reference, type, range, Eval, URI, and custom errors.

If you type something that is against the syntax rules, you will be shown syntax errors.
If you type an inappropriate value, the language will show you type errors.,
Range error occurs when you set a range but type a value beyond the range.
If you write the eval() function inappropriately, it will show eval errors.
Like Eval error, this type of error occurs when you type the URI() function wrong.
If you declare a variable that is not mentioned in the scope, reference errors occur.
Custom errors are developed to fix some portions of an application.

9. What is the purpose of the Constructor function?

If you want to create and initialize objects in JavaScript, You can use a special function named Constructor Function. Developers can call this function by typing “new”. You can add multiple prototypes to the object by using this function.

10. What is recursion in JavaScript?

Recursion is an important mechanism in any programming language. Recursion occurs when a function calls itself to execute a code. If you construct your code in a tree structure to solve a problem, It becomes easier.

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