Advanced JavaScript Interview Questions & Answers in…

HARDEST JavaScript Interview Question Ever! Part 1

Q29. What is the difference between null & undefined?

Undefined means a variable has been declared but has not yet been assigned a value. On the other hand, null is an assignment value. It can be assigned to a variable as a representation of no value. Also, undefined and null are two distinct types: undefined is a type itself (undefined) while null is an object.

Q6. What are the advantages of JavaScript?

JavaScript advantages - JavaScript interview questionsFollowing are the advantages of using JavaScript −

  • Less server interaction − You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.
  • Immediate feedback to the visitors − They don’t have to wait for a page reload to see if they have forgotten to enter something.
  • Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.
  • Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.
  • Q11: Explain what is hoisting in Javascript

    Hoisting is the concept in which Javascript, by default, moves all declarations to the top of the current scope. As such, a variable can be used before it has been declared.

    Note that Javascript only hoists declarations and not initializations.

    Q8. How can you create an Array in JavaScript?

    You can define arrays using the array literal as follows-

    6. How do you calculate Fibonacci numbers in JavaScript?

    Creating Fibonacci numbers is a very popular question for programmers. Try to answer it correctly with an efficient code example.

    Example: “Fibonacci number sequence is a numbers sequence where each value is the sum of the previous two, starting with 0 and 1. The first seven values are 0, 1, 1, 2, 3, 5, 8. This JavaScript function will return Fibonacci numbers sequence up to a given numbers of terms.”

    // ask for input from the user const number = parseInt(prompt(Enter the no. of terms: )); let n1 = 0, n2 = 1, nextNumber; console.log(Fibonacci Sequence:); for (let i = 1; i <= number; i++) { console.log(n1); nextTerm = n1 + n2; n1 = n2; n2 = nextNumber; }

    Q37. What do you mean by Imports and Exports?

    Exports and Imports specially assist us in writing modular JavaScript code. Using these, we can easily split our code into various files. Imports enables us taking only particular variables or procedures of a file. We can simply import variables or methods that are exported by a module. Following is the example for more details.

    Q25. What are the ways to define a variable in JavaScript?

    The three possible ways of defining a variable in JavaScript are:

  • Var – The JavaScript variables statement is used to declare a variable and, optionally, we can initialize the value of that variable. Example: var a =10; Variable declarations are processed before the execution of the code.
  • Const – The idea of const functions is not allow them to modify the object on which they are called. When a function is declared as const, it can be called on any type of object.
  • Let – It is a signal that the variable may be reassigned, such as a counter in a loop, or a value swap in an algorithm. It also signals that the variable will be used only in the block it’s defined in.
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