Variable names should not be identical to the reserved keywords. The ES6 version of Javascript introduced the rest parameter and spread operator. For declaring a class, the class keyword must be followed by the class name. Class expressions are one of the ways to define classes.

This has different values depending on where it is used. In a method, this refers to the owner object and in a function, this refers to the global object. Today, Google and Facebook use JavaScript to build complex, desktop-like web applications.

What is the use of the isNaN function?

If the JavaScript code set the timer to 2 minutes and when the times are up then the page displays an alert message “times up”. The setTimeout() method calls a function or evaluates an expression after a specified number of milliseconds. JavaScript is the most popular lightweight, interpreted compiled programming language. It can be used for both Client-side as well as Server-side developments. JavaScript is also known as a scripting language for web pages. Semantic HTML is processed by traditional web browsers and many other user agents.

  • Here are JavaScript interview questions and answers for fresher as well as experienced candidates to get their dream job.
  • IsNan function is useful in case the argument is not a number.
  • The event loop continuously checks for new events in the event queue.
  • This is a useful strategy for ensuring that an object has a given set of properties.
  • A Mixin is a code block that lets the group of CSS declarations which we can reuse in our site.
  • You can export variables by using the export keyword in front of the variable declaration.

Below is a list of JavaScript interview questions and answers that may be asked during a job interview. Candidates are likely to be asked javascript basic interview questions to advance the interview, depending on their experience and various other factors. Undeclared variables are those that do not exist in a program and are not declared. If the program tries to read the value of an undeclared variable, then a runtime error is encountered. Undefined variables are those that are declared in the program but have not been given any value.

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Now let’s move on to the next section of JavaScript interview questions. You can use strings’ split() function to break the string into key and values. You should not use any of the JavaScript reserved keyword as variable name. For example, break or boolean variable names are not valid. Let’s begin with the first section of JavaScript interview questions.

Let’s imagine that I only focus on high-level topics that can be learned only through experience, such as finding the folder structure, architecture, testing approaches, etc. The conversation for sure would be interesting, but, as a recruiter, I wouldn’t be sure if the candidate was able to write good code. These are some of the key steps involved in developing a UI from scratch. However, the exact process can vary depending on the project requirements, resources, and timeline. The event loop continues to execute events from the queue, and once it reaches the “fetch” event, it initiates the network request. The callback function updates the webpage with new content and makes an asynchronous network request to fetch additional data.

What is the method for reading and writing a file in JavaScript?

During the execution of the callback function, other events can be added to the queue. The event loop continuously checks for new events in the event queue. It’s important to note that the choice of JavaScript framework ultimately depends on various factors, including project requirements, team skill set, and personal preferences. Evaluating each framework’s strengths and weaknesses is essential to determine which is the best fit for your project. For small projects where the application is simple and doesn’t require a lot of complex functionality, React or Vue would be good choices.

It is also possible to erase a specific portion of coding simply and without accessing any other command for this. An object in JavaScript is a collection of properties containing primitive data types, such as strings, numbers, booleans, and functions. Objects are used to model real-world entities and help organize code into reusable components. Global variables are available throughout the length of the code so that it has no scope.

Q42. What will be the output of the code below?

Additionally, wherever the code occurs in a single line only, we can omit the curly braces. If there is only one argument in a function, then we can omit even the () parenthesis. Through Active X objects and by using the JavaScript extensions it is possible to read and write the file in JavaScript.

senior javascript developer interview questions

These 2 languages ​​are not at all interdependent and are intended for different purposes. Java is Object Oriented Programming or structured programming languages ​​such as C++ or C, whereas JavaScript is a client-side scripting language. hire javaScript developer It is a client-side and server-side scripting language that is inserted into HTML pages and understood by web browsers. JavaScript is also an object-oriented programming language. Here, emp1 object has company as its prototype property.

Q27. What is the difference between Local storage & Session storage?

On the other hand, the Native Objects are the standard built-in objects provided by JavaScript. A callback function is a function that is passed as an argument to another function and ensures that a function is not going to run before a task is completed. This function runs right after the task has been completed. But if you’re feeling overwhelmed by all the resumes, technical interviews, coding challenges, and general frustrations of the hiring process, you’re not alone. JavaScript examplesdemonstrating the language’s capability in web applications, mobile applications, and even games. You probably recognize these logical operators from an elementary math class years ago.

senior javascript developer interview questions