Both can be used to change the context of a function invocation, which allows for some interesting use cases such as borrowing methods from other objects. A closure is a function that has access to variables in its parent scope even after the parent function has returned. Closures are commonly used in JavaScript for encapsulating data and abstracting details of implementation. Is used to compare two variables, but this will check strict type, which means it will check the data type and compare two values. While in Strict mode, all variables have to be declared explicitly, values cannot be assigned to a read-only property, etc.

javascript developer interview questions

And with the launch of node.js, it has become one of the top languages for building server-side applications. However, the web still needs to be bigger to utilize JavaScript’s full potential and flexibility. Modules should be Immediately-Invoked-Function-Expressions to allow for private scopes — that is, a closure that protects variables and methods . This approach avoids interruption of the user experience between successive pages, making the application behave more like a desktop application. A resource is the fundamental concept of Restful architecture. A resource is an object with a type, relationship with other resources and methods that operate on it.

What is the === operator?

It’s always pass by value, but for objects the value of the variable is a reference. Because of this, when you pass an object and change its members, those changes persist outside of the function. But if you actually change the value of the object variable you will see that the change does not persist, proving it’s really pass by value. WeakMap allows garbage collector to do its task but not Map.

javascript developer interview questions

Mainly, the var keyword is used to declare a global or local variable. Finding the right candidates and hiring qualified JavaScript developers can be a prolonged process. Because of its popularity, JavaScript developers are in high demand. The TDZ is the state where the variables “let” and “constr” can’t be reached. Variables exist in the TDZ from the place they get bound until they’re declared. The window is the first object that gets loaded into the browser.

What are the various data types that exist in JavaScript?

A NAN method is used to return a true value if the variable has no number. SetTimeout() – This method helps to perform certain operations after a specified time like evaluating expressions and calling functions. Const- A constant variable is assigned with one value only once before the execution of code. The callback is a typical function of JavaScript that can be passed as an option or argument of JavaScript.

Constructor functions are used to create single objects or multiple objects with similar properties and methods. Following are the different object prototypes in javascript that are used to inherit particular properties and methods from the Object.prototype. The problems faced by using global variables are the clash of variable names of local and global scope. Also, it is difficult to debug and test the code that relies on global variables. When you use strict mode, you cannot use implicitly declared variables, or assign a value to a read-only property, or add a property to an object that is not extensible.

Junior Javascript Developer Interview Questions

It initializes a queue with the root node and an empty result array. Then it enters a while loop, where it dequeues the first element in the queue , adds its value to the result array, and enqueues its left and right children . If the function has not returned false by this point, the two strings must be anagrams, and the function returns true. The difference between the two methods is that call() accepts an argument list, while apply() accepts an array of arguments.

  • The rest parameter can also be used to extract any or all parts of an argument.
  • These two languages are not at all inter-dependent and are designed for different intent.
  • Turing helps companies match with top quality remote JavaScript developers from across the world in a matter of days.
  • Variables that are not declared or that do not exist in a program or application.
  • If you try to read an undeclared variable, JavaScript throws an error.
  • Also, it isn’t easy to debug and test code based on globals.

Tell us the skills you need and we’ll find the best developer for you in days, not weeks. Turing helps companies match with top quality remote JavaScript developers from across the world in a matter of days. Scale your engineering team with pre-vetted JavaScript developers at the push of a buttton. Window.onload is an event that is fired when the page has finished loading.

Java Developer Job Description

To read a cookie value, you call the cookie property of the document object. Functions capable of accepting other functions as arguments and able to return functions as their return value. JavaScript is a popular web scripting language that’s used for client-side and server-side development. JavaScript can be inserted into hire javaScript developer HTML pages and executed by web browsers. Whether you’re a JavaScript newbie or an experienced engineer that’s ready for a new challenge at a new company, preparing for interviews can be nerve-wracking! But if you prepare well with interview questions for JavaScript, you’ll be confident and ready for whatever they may ask.

javascript developer interview questions

This has led to high demand for JavaScript developers and a proliferation of free and paid courses promising to teach people JavaScript in just a few weeks. The quality of these courses varies greatly, so you’ll need to carefully vet JavaScript developers before you hire there. The this keyword is a self-reference for JavaScript objects.

Essential JavaScript Interview Questions *

If the program tries to read the value of an undefined variable, an undefined value is returned. The type of operator is used to get the data type of its operand. The operand can be either a literal or a data structure such as a variable, a function, or an object. It is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand.

javascript developer interview questions


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