Interviewing for a position as a JavaScript developer? Here are 21 essential questions that you need to know the answer to. The following will be a short explanation, along with some solutions, of a popular JavaScript question that tends to get asked in developer. Dear readers, these JavaScript Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during.


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There are a couple ways we can use to empty an array, so let's discuss them all. This is recommended if you don't have references to the original array arrayList anywhere else, because it will actually create a new, empty array.

You should be careful with this method of emptying the array, because if you have referenced this array from another variable, then the original reference array will remain unchanged.

This way of emptying the array also updates all the interview question on javascript variables that point to the original array.

Therefore, this method is useful when you want to update all reference variables pointing to arrayList. This way of emptying the array will also update all the references to the original array. Question 7 How do you check if an object is an array or not?

Typescript adds interview question on javascript features like Interfaces, Generics, etc. There are many Javascript Frameworks available today, but the most commonly used frameworks are: The operator typeof is an example of Unary Operators, which is used by placing it before its operand; which can be of any type.

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An anonymous function allows a developer to create a function that has no name. In other words, anonymous functions can be used to store a bit of functionality in a variable and pass that piece of functionality around.

Anonymous functions exist only after they are called; whereas, Named functions to exist even if not called. Interview question on javascript functions are executed right after its definition.

The callback function is a mechanism to send one function to another function as an argument; i.

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The calling of recursion is possible in two functions, but the call comes to an end after some time. The inner functions can be called as closure when it has access to the outer function's variables. The interview question on javascript code is something that should be finished before anything else can happen, or in other words, the synchronous code is blocking.


And the Asynchronous code is something in which actions can happen and is not dependent on other actions- in other words, it is non-blocking. There are three types of pop up boxes in Javascript i alert provides some information to the user with just an OK button ii confirm asks a question to the user with two options Ok and cancel, and iii prompt takes an input from the interview question on javascript.

But, when used outside a function, it refers to the window object.

With the latest version of Javascript, exception handling is possible; and this can be achieved using the following keywords try, catch and finally. The typeof operator returns a string of what type the operand is.

Whereas, the instanceof operator does not work with primitive data types; but works with objects and checks interview question on javascript what type the object is.

Top 85 JavaScript Interview Questions & Answers

All the elements or nodes are part of window. Using BOM interaction with a browser is possible. Default object of the browser is a window.