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Top 100 Javascript interview questions

  1. What is JavaScript and how is it used?
  2. What is the difference between var, let, and const?
  3. How do you declare a function in JavaScript?
  4. How do you define an object in JavaScript?
  5. What is the difference between null and undefined in JavaScript?
  6. What is the difference between == and === in JavaScript?
  7. What is an anonymous function in JavaScript?
  8. What is a callback function in JavaScript?
  9. What is a promise in JavaScript?
  10. What is a closure in JavaScript?
  11. What is the difference between a class and an object in JavaScript?
  12. What is the difference between a function and a method in JavaScript?
  13. What is the difference between synchronous and asynchronous code in JavaScript?
  14. What is a higher-order function in JavaScript?
  15. What is the difference between a for loop and a for-in loop in JavaScript?
  16. What is the difference between a for-of loop and a for-in loop in JavaScript?
  17. What is the difference between a for loop and a while loop in JavaScript?
  18. What is a do-while loop in JavaScript?
  19. What is the difference between break and continue in JavaScript?
  20. What is the difference between a switch statement and an if-else statement in JavaScript?
  21. What is the difference between an array and an object in JavaScript?
  22. What is the difference between an object literal and a constructor function in JavaScript?
  23. How do you create an array in JavaScript?
  24. How do you access elements in an array in JavaScript?
  25. How do you add elements to an array in JavaScript?
  26. How do you remove elements from an array in JavaScript?
  27. How do you loop through an array in JavaScript?
  28. How do you sort an array in JavaScript?
  29. How do you reverse an array in JavaScript?
  30. How do you search an array in JavaScript?
  31. How do you slice an array in JavaScript?
  32. How do you concatenate arrays in JavaScript?
  33. How do you merge arrays in JavaScript?
  34. How do you find the intersection of arrays in JavaScript?
  35. How do you find the difference between arrays in JavaScript?
  36. How do you create a copy of an array in JavaScript?
  37. How do you check if an element exists in an array in JavaScript?
  38. How do you check if an array is empty in JavaScript?
  39. How do you check if an array is an array in JavaScript?
  40. How do you check if an element is in an array in JavaScript?
  41. How do you check if an element is not in an array in JavaScript?
  42. How do you check if an array includes an element in JavaScript?
  43. How do you check if an array does not include an element in JavaScript?
  44. How do you check if an array is equal to another array in JavaScript?
  45. How do you check if an array is not equal to another array in JavaScript?
  46. How do you check if an array is a subset of another array in JavaScript?
  47. How do you check if an array is a superset of another array in JavaScript?
  48. How do you check if an array is the same as another array in JavaScript?
  49. How do you check if an array is not the same as another array in JavaScript?
  50. What is the purpose of the “this” keyword in JavaScript?
  51. What is a prototype in JavaScript?
  52. How do you extend a class in JavaScript?
  53. What is inheritance in JavaScript?
  54. What is a constructor function in JavaScript?
  55. What is the purpose of the new keyword in JavaScript?
  56. What is the difference between a constructor function and a class in JavaScript?
  57. What is a static method in JavaScript?
  58. What is a singleton pattern in JavaScript?
  59. What is a module in JavaScript?
  60. What is the purpose of the module pattern in JavaScript?
  61. What is the difference between a module and a namespace in JavaScript?
  62. What is the purpose of the import keyword in JavaScript?
  63. What is the purpose of the export keyword in JavaScript?
  64. What is the difference between a default export and a named export in JavaScript?
  65. What is a generator function in JavaScript?
  66. What is the purpose of the yield keyword in JavaScript?
  67. What is the purpose of the spread operator in JavaScript?
  68. What is the purpose of the rest parameter in JavaScript?
  69. What is the purpose of the Array.from() method in JavaScript?
  70. What is the purpose of the Array.of() method in JavaScript?
  71. What is the purpose of the Array.fill() method in JavaScript?
  72. What is the purpose of the Array.copyWithin() method in JavaScript?
  73. What is the purpose of the Array.find() method in JavaScript?
  74. What is the purpose of the Array.findIndex() method in JavaScript?
  75. What is the purpose of the Array.entries() method in JavaScript?
  76. What is the purpose of the Array.keys() method in JavaScript?
  77. What is the purpose of the Array.values() method in JavaScript?
  78. What is the purpose of the Array.includes() method in JavaScript?
  79. What is the purpose of the Array.flat() method in JavaScript?
  80. What is the purpose of the Array.flatMap() method in JavaScript?
  81. What is the purpose of the Array.reduce() method in JavaScript?
  82. What is the purpose of the Array.reduceRight() method in JavaScript?
  83. What is the purpose of the Array.sort() method in JavaScript?
  84. What is the purpose of the Array.reverse() method in JavaScript?
  85. What is the purpose of the Array.concat() method in JavaScript?
  86. What is the purpose of the Array.slice() method in JavaScript?
  87. What is the purpose of the Array.splice() method in JavaScript?
  88. What is the purpose of the Array.join() method in JavaScript?
  89. What is the purpose of the Array.toString() method in JavaScript?
  90. What is the purpose of the Array.toLocaleString() method in JavaScript?
  91. What is the purpose of the Array.indexOf() method in JavaScript?
  92. What is the purpose of the Array.lastIndexOf() method in JavaScript?
  93. What is the purpose of the Array.every() method in JavaScript?
  94. What is the purpose of the Array.some() method in JavaScript?
  95. What is the purpose of the Array.forEach() method in JavaScript?
  96. What is the purpose of the Array.map() method in JavaScript?
  97. What is the purpose of the Array.filter() method in JavaScript?

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