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Javascript Interviews Questions

SELECT * FROM `itio_interview_question` WHERE `tutorial_menu`='11' AND `tutorial_status`=1

Interviews Questions - (Javascript)

Fundamentals

  1. What is JavaScript?

    • JavaScript is a high-level, interpreted programming language primarily used to add interactivity and dynamic behavior to web pages.  
  2. What are the core components of JavaScript?

    • ECMAScript: The standardized specification for JavaScript.
    • DOM (Document Object Model): Represents the structure and content of an HTML or XML document as a tree of objects.
    • BOM (Browser Object Model): Represents the browser window and its components (e.g., history, location, navigator).
  3. How do you include JavaScript in an HTML document?

    • Inline: Within the <script> tag within the HTML.
    • External: Linking to a separate JavaScript file using the <script src="..."></script> tag.
  4. What are variables in JavaScript?

    • Containers for storing data values. Declared using let, const, or var.
  5. What are data types in JavaScript?

    • Primitive: Number, String, Boolean, Null, Undefined, Symbol.
    • Object: Complex data types like arrays, objects, functions.

Data Structures

  1. What are arrays in JavaScript?

    • Ordered collections of values.
  2. How do you access elements in an array?

    • Using array indices (e.g., array[0] for the first element).
  3. What are objects in JavaScript?

    • Collections of key-value pairs.
  4. How do you access properties of an object?

    • Using dot notation (e.g., object.property) or bracket notation (e.g., object['property']).

Control Flow

  1. What are conditional statements in JavaScript?

    • if, else if, else.
  2. What are loops in JavaScript?

    • for, while, do...while, for...of, for...in.
  3. What are functions in JavaScript?

    • Reusable blocks of code that perform a specific task.
  4. What are function arguments and parameters?

    • Parameters are placeholders defined in the function declaration.
    • Arguments are the actual values passed to the function when it's called.

Operators

  1. What are the different types of operators in JavaScript?

    • Arithmetic, comparison, logical, assignment, bitwise.
  2. What is the difference between == and === in JavaScript?

    • == performs type coercion (e.g., "1" == 1 is true).
    • === performs strict comparison (e.g., "1" === 1 is false).

DOM Manipulation

  1. What is the Document Object Model (DOM)?

    • Represents the structure of an HTML or XML document as a tree of objects.
  2. How do you select HTML elements using JavaScript?

    • Using methods like getElementById(), getElementsByClassName(), querySelector(), and querySelectorAll().
  3. How do you change the content of an HTML element using JavaScript?

    • Access the element's innerHTML or textContent property.
  4. How do you add, remove, or modify HTML elements using JavaScript?

    • Using methods like createElement(), appendChild(), removeChild(), insertBefore().
  5. How do you handle events in JavaScript?

    • Using event listeners (e.g., addEventListener()).

Events

  1. What are common JavaScript events?

    • click, mouseover, mouseout, keydown, keyup, submit, load.
  2. How do you prevent the default behavior of an event?

    • Use event.preventDefault().

JavaScript Objects

  1. What is the this keyword in JavaScript?

    • Refers to the current object within a method.
  2. What are constructors in JavaScript?

    • Special methods used to create and initialize objects.
  3. What are prototypes in JavaScript?

    • Allow you to add properties and methods to objects after they are created.

Arrays

  1. How do you add elements to an array in JavaScript?

    • Using push(), unshift(), splice().
  2. How do you remove elements from an array in JavaScript?

    • Using pop(), shift(), splice().
  3. How do you iterate over an array in JavaScript?

    • Using for, for...of, forEach().

Strings

  1. How do you manipulate strings in JavaScript?
    • Using methods like concat(), slice(), split(), join(), toUpperCase(), toLowerCase().

JSON

  1. What is JSON?

    • JavaScript Object Notation, a lightweight data-interchange format.
  2. How do you parse JSON data in JavaScript?

    • Using JSON.parse().
  3. How do you stringify JavaScript objects into JSON?

    • Using JSON.stringify().

Asynchronous JavaScript

  1. What are callbacks in JavaScript?

    • Functions that are passed as arguments to other functions and executed later.
  2. What are promises in JavaScript?

    • Represent the eventual completion (or failure) of an asynchronous operation and its resulting value.  
  3. What is async/await?

    • A syntax for writing asynchronous code in a more synchronous-like manner.

Error Handling

  1. How do you handle errors in JavaScript?
    • Using try...catch...finally blocks.

DOM Manipulation

  1. How do you create a new HTML element using JavaScript?

    • document.createElement()
  2. How do you add event listeners to HTML elements?

    • element.addEventListener('event', callback)
  3. How do you modify the CSS styles of an element using JavaScript?

    • Access the style property of the element.
  4. How do you get and set the value of an input field using JavaScript?

    • Access the value property of the input element.

JavaScript Libraries and Frameworks

  1. What is jQuery?

    • A popular JavaScript library that simplifies HTML traversal, event handling, and AJAX.
  2. What is React?

    • A JavaScript library for building user interfaces.
  3. What is Angular?

    • A full-featured JavaScript framework for building web applications.
  4. What is Vue.js?

    • A progressive framework for building user interfaces.

Advanced Topics

  1. What are closures in JavaScript?

    • Functions that have access to variables from the outer (enclosing) function's scope, even after the outer function has finished executing.
  2. What is hoisting in JavaScript?

    • The process of moving variable declarations to the top of their scope during compilation.
  3. What is the difference between let, const, and var?

    • let and const are block-scoped, while var is function-scoped.
    • let allows reassignment, while const does not.
  4. What are arrow functions in JavaScript?

    • A concise syntax for writing functions.
  5. What is the this keyword in the context of arrow functions?

    • this refers to the surrounding object in arrow functions, not the object that the function is called on.
  6. How can you improve the performance of your JavaScript code?

    • Minimize DOM manipulation, use efficient algorithms, avoid unnecessary calculations, and optimize for garbage collection.

I hope these questions are helpful for your JavaScript interview preparation!

Disclaimer for AI-Generated Content:
The content provided in these tutorials is generated using artificial intelligence and is intended for educational purposes only.

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