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Q1. What is JavaScript?
ANS. JavaScript is a high-level, interpreted programming language primarily used for building interactive web applications.

Q2. What are the data types in JavaScript?
ANS. Primitive data types: number, string, boolean, null, undefined, symbol. Non-primitive data type: object.

Q3. What is the difference between == and operators in JavaScript?
ANS. == checks for equality after type coercion, while === checks for equality without type coercion.

Q4. What is hoisting in JavaScript?
ANS. Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their containing scope during compilation.

Q5. What is closure in JavaScript?
ANS. A closure is the combination of a function bundled together with references to its surrounding state, allowing it to retain access to variables from its lexical scope even when called outside that scope.

Q6. Explain event delegation in JavaScript.
ANS. Event delegation is a technique of handling events at a higher level in the DOM tree and letting events propagate to their target element.

Q7. What is a promise in JavaScript?
ANS. A promise represents the eventual completion or failure of an asynchronous operation, and its resulting value.

Q8. What is the purpose of this keyword in JavaScript?
ANS. This refers to the object to which a function or method belongs or the object that is currently being operated on.

Q9. What is a callback function in JavaScript?
ANS. A callback function is a function passed as an argument to another function, which is then invoked inside the outer function to complete some kind of routine or action.

Q10. What is event bubbling in JavaScript?
ANS. Event bubbling is the process where an event propagates through the DOM tree from the innermost target element up to the document root.

ANS. Q11. Explain the concept of prototypal inheritance in JavaScript.
ANS. Prototypal inheritance is a way of creating objects based on other objects, where objects inherit properties and methods directly from other objects.

Q12. What is the purpose of the bind method in JavaScript?
ANS. The bind method creates a new function that, when called, has its this keyword set to a specific value.

Q13. What is the difference between null and undefined in JavaScript?
ANS. null is an intentional absence of any value, while undefined means a variable has been declared but has not yet been assigned a value.

Q14. What is the purpose of the let keyword in JavaScript?
ANS. The let keyword declares block-scoped variables, which means the variable is only accessible within the block it is defined in.

Q15. What is the purpose of the const keyword in JavaScript?
ANS. The const keyword declares variables that cannot be re-assigned a new value once initialized.

Q16. What is an arrow function in JavaScript?
ANS. An arrow function is a shorthand syntax for writing function expressions, providing a more concise way to define functions.

Q17. Explain the concept of asynchronous programming in JavaScript.
ANS. Asynchronous programming allows code to run non-sequentially, enabling tasks to be executed concurrently and improving performance by not blocking the main execution thread.

Q18. What is the forEach method in JavaScript?
ANS. The forEach method executes a provided function once for each array element.

Q19. What is the difference between var, let, and const
ANS. var declares variables with function scope, let declares variables with block scope, and const declares variables that cannot be reassigned.

Q20. What are some ways to handle asynchronous code in JavaScript
ANS. Callbacks, Promises, Async/Await.

Q21. What is the event loop in JavaScript?
ANS. The event loop is a single-threaded mechanism that processes tasks in a queue, handling asynchronous operations like callbacks, promises, and I/O operations.

Q22. Explain the difference between document.ready() and window.onload() in JavaScript.
ANS. document.ready() is an event that fires when the DOM is fully loaded, while window.onload() is an event that fires when all assets have loaded.

Q23. What is a higher-order function in JavaScript?
ANS. A higher-order function is a function that takes one or more functions as arguments or returns a function as its result.

Q24. What is the purpose of the map method in JavaScript?
ANS. The map method creates a new array with the results of calling a provided function on every element in the calling array.

Q25. What is the difference between Object.keys() and Object.values()?
ANS. Object.keys() returns an array of a given object's own enumerable property names, while Object.values() returns an array of a given object's own enumerable property values.

Q26. Explain the concept of destructuring in JavaScript.
ANS. Destructuring is a JavaScript expression that allows extracting data from arrays, objects, and function parameters and binding it to variables.

Q27. What is the purpose of the find method in JavaScript?
ANS. The find method returns the first element in an array that satisfies the provided testing function.

Q28. What is the difference between == and operators in JavaScript
ANS. performs type coercion before checking equality, while strictly checking for equality without type conversion.

Q29. What is the purpose of the reduce method in JavaScript?
ANS. The reduce method applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

Q30. What is the purpose of the filter method in JavaScript?
ANS. The filter method creates a new array with all elements that pass the test implemented by the provided function.

Q31. What is the purpose of the some method in JavaScript?
ANS. The some method tests whether at least one element in the array passes the test implemented by the provided function.

Q32. What is the purpose of the every method in JavaScript?
ANS. The every method tests whether all elements in the array pass the test implemented by the provided function.

Q33. What is the difference between setTimeout and setinterval functions in JavaScript?
ANS. setTimeout executes a function once after a specified time interval, while setinterval repeatedly executes a function at specified time intervals.

Q34. What is the purpose of the slice method in JavaScript?
ANS. The slice method returns a shallow copy of a portion of an array into a new array object selected from start to end (end not included).

Q35. What is the purpose of the splice method in JavaScript?
ANS. The splice method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

Q36. What is a generator function in JavaScript?
ANS. A generator function is a special type of function that can pause and resume its execution, allowing iterative algorithms to be written in a more intuitive way.

Q37. What is the purpose of the Symbol data type in JavaScript?
ANS. The Symbol data type represents a unique and immutable value that may be used as the key of an Object property.

Q38. What is the arguments object in JavaScript?
ANS. The arguments object is an array-like object accessible inside functions that contains the values of the arguments passed to that function

Q39. What is the purpose of the String.prototype.split() method in JavaScript?
ANS. The split() method splits a string object into an array of strings by separating the string into substrings.

Q40. What is the purpose of the String.prototype.trim() method in JavaScript?
ANS. The trim() method removes whitespace from both ends of a string

Q41. What is the purpose of the String.prototype.replace() method in JavaScript?
ANS. The replace() method returns a new string with some or all matches of a pattern replaced by a replacement.

Q42. What is the purpose of the String.prototype.charAt() method in JavaScript?
ANS. The charAt() method returns the character at a specified index in a string.

Q43. What is the purpose of the String.prototype.concat() method in JavaScript?
ANS. The concat() method concatenates the string arguments to the calling string and returns a new string.

Q44. What is the purpose of the String.prototype.indexOf() method in JavaScript?
ANS. The indexOf() method returns the position of the first occurrence of a specified value in a string.

Q45. What is the purpose of the String.prototype.toUpperCase() method in JavaScript?
ANS. The toUpperCase() method returns the calling string value converted to uppercase.

Q46. What is the purpose of the String.prototype.toLowerCase() method in JavaScript?
ANS. The toLowerCase() method returns the calling string value converted to lowercase.

Q47. What is the purpose of the String.prototype.slice() method in JavaScript?
ANS. The slice() method extracts a section of a string and returns it as a new string.

Q48. What is the purpose of the String.prototype.substr() method in JavaScript?
ANS. The substr() method returns the characters in a string beginning at the specified location through the specified number of characters.

Q49. What is the purpose of the String.prototype.startsWith() method in JavaScript?
ANS. The startsWith() method determines whether a string begins with the characters of a specified string returning true or false as appropriate.

Q50. What is the purpose of the String.prototype.endsWith() method in JavaScript?
ANS. The endsWith() method determines whether a string ends with the characters of a specified string, returning true or false as appropriate.