The reduce() function is used to reduce an array to a single value by applying a function to each element and accumulating the result. Both localStorage and sessionStorage are web storage objects in JavaScript, but they have different scopes and lifetimes. The setTimeout() function is used to delay the execution of a function or the evaluation of an expression after a specified amount of time in milliseconds. Arrow functions are a concise syntax for writing JavaScript functions.

Each question will have answers and examples you can use to prepare for your own interview. Immutability, as we mentioned, is one of the core features of functional programming. Immutability refers to the property of an object to not be modifiable after it is created. Immutability, as a concept, allows you to prevent unexpected consequences like mutating objects.

What is the use of the blur function?

DOM is required for developing web pages, which includes objects like paragraphs, links, etc. These objects can be operated to include actions like add or delete. On top of that, the use of API gives an advantage over other existing models.

Try reading the question and answering for yourself before reading on to see how you did. There are of course ways to avoid mutation in the sort function, but in our example, it will lead to more lines of codes, which is not practical at all. The reason is that the ‘sort function’ lists things in ascending order by default. This final solution will prove your future employer that you genuinely know what you’re doing and you are really taking the right steps to be a hotshot developer. Then, the ‘map’ function will come in, eventually giving us a brand new array showing the vegetarian / vegan passengers only. As a matter of fact, the ‘forEach’ function handles the problem similarly.

JavaScript Coding Interview Questions for Beginner, Mid-Level and Expert Developers

Along with CSS and HTML, it is the backbone of nearly every website’s user interface (UI). Hiring developers is often a more painstaking task than the hiring process in other fields. To assess technical and functional skills required by a competent JavaScript Developer, check out iMocha’s coding skill tests library. Name some of the built-in methods and the values returned by them.

JavaScript is a leading programming language for creating interactive and dynamic web pages. You will see a lot of popular frameworks and libraries based on JavaScript, such as jQuery, VueJS, ReactJS, AngularJS and others. It is no surprise that JavaScript is the main programming language for the front-end development of software applications. This is not to say that functional programming is the be-all and end-all of all programming.

Top 50 JavaScript Developer Interview Questions to Select the Best Candidate

This function takes an array as an argument and uses the sort() method to sort the elements of the array in ascending order. The sort() method sorts the elements of an array in place and returns the sorted array. In the code above, both in the global scope and functional scope, we are trying to access variables that have not been declared yet. A callback is a function that will be executed after another function gets executed.

The following one line function will return true if str is a palindrome; otherwise, it returns false. Asynchronous functions, on the other hand, execute each line of code without stopping to wait for a value from a function. An asynchronous function usually depends on a Promise or a callback https://www.globalcloudteam.com/ which executes while the main program is running. The Promise or callback will return a value back to the main program. First, the “if” statement makes sure that an array has been defined. Without this check, our code would return an error if “array_name” could not be found.

Name two principle programming paradigms for JavaScript development.

Note this is one of those JavaScript coding interview questions that’s good to know. An undefined variable has been declared in the program, but no value has been assigned. This means the variable exists, but its value is yet to be defined.

Unit tests in Cypress can be executed without running a web server, making it ideal for testing a JavaScript/TypeScript library meant to be used in the browser. Jasmine is a JavaScript behavior-driven development (BDD) test framework. What this means is that Jasmine adopts a user-first approach to testing, in contrast to a developer-first approach.

Describe the various ways to create an array object in JavaScript.

When a value of zero is passed as the second argument to setTimeout(), it attempts to execute the specified function “as soon as possible”. Specifically, execution of the function is placed on the event queue to occur on the next timer tick. Note, though, that this is not immediate; the function https://www.globalcloudteam.com/how-to-hire-a-javascript-developer/ is not executed until the next tick. An efficient way to filter values out of an array of objects is to use the JavaScript filter() function. The filter function iterates through a list of items and creates a new list of items that meet a particular condition or set of conditions.

• JavaScript is also being used widely in game development and Mobile application development.
• An interview can be a very useful tool as well, but don’t waste time asking about syntax or language quirks.
• An undefined variable has been declared in the program, but no value has been assigned.
• An event handler is required to manage the proper execution of all these events.
• JavaScript has emerged as the cornerstone of modern web development, enabling dynamic and interactive experiences that shape the digital landscape.

If the program tries to read the value of an undefined variable, an undefined value is returned. The main difference between var and let is the scope of the variables they create. Variables declared with var have function scope, which means they are accessible throughout the function in which they are declared. Variables declared with let have block scope, which means they are only accessible within the block where they are declared.

What is the difference between synchronous and asynchronous functions?

Arrow functions accept arguments just like a regular function expression. You do not need to use a return statement with an arrow function. This is because arrow functions implicitly return a value if there is only one value to return.