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JavaScript Interview Questions and Answers

  Difficulty Level: AllBeginnerIntermediateExperienced/Expert

Ques 1. What are JavaScript data types?

Ques 2. How do you convert numbers between different bases in JavaScript?

Ques 3. What does isNaN function do?

Ques 4. What looping structures are there in JavaScript?

Ques 5. What boolean operators does JavaScript support?

Ques 6. How do you create a new object in JavaScript?

Ques 7. How about 2+5+"8"?

Ques 8. What does "1"+2+4 evaluate to?

Ques 9. How do you assign object properties?

Ques 10. What's a way to append a value to an array?

Ques 11. What's relationship between JavaScript and ECMAScript?

Ques 12. What is negative infinity?

Ques 13. What is this keyword?

Ques 14. What is Javascript?

Ques 15. What is identifier in Javascript?

Ques 16. What type of variables are in Javascript?

Ques 17. What is Assignment Operator in Javascript?

Ques 18. What is Expression in Javascript?

Ques 19. Explain String in Javascript?

Ques 20. What is Date class in Javascript? Please explain.

Ques 21. What are Math routines in Javascript?

Ques 22. Write a javascript to get difference between two dates.

Ques 23. What about Navigator object?

Ques 24. What is User-Defined class in Javascript?

Ques 25. Few events in Javascript.

Ques 26. Explain String functions in Javascript.

Ques 27. Tell us about local variables.

Ques 28. Explain Global Variables in Javascript.

Ques 29. What are primitives in Javascript?

Ques 30. How do you submit a form using Javascript?

Ques 31. How do we get JavaScript onto a web page?

Ques 32. How can JavaScript make a Web site easier to use? That is, are there certain JavaScript techniques that make it easier for people to use a Web site?

Ques 33. How to create arrays in JavaScript?

Ques 34. Where are cookies actually stored on the hard disk?

Ques 35. How to set a HTML document's background color?

Ques 36. Are you concerned that older browsers don't support JavaScript and thus exclude a set of Web users or individual users?

Ques 37. What does isNaN function do?

Ques 38. Methods GET and POST in HTML forms - what's the difference?

Ques 39. How to write a script for "Select" lists using javascript?

Ques 40. What does the "Access is Denied" IE error mean?

Ques 41. Is a Javascript script faster than an ASP script?

Ques 42. How to get the contents of an input box using Javascript?

Ques 43. How to determine the state of a checkbox using Javascript?

Ques 44. How to set the focus in an element using Javascript?

Ques 45. What is the difference between an alert box and a confirmation box?

Ques 46. What is a prompt box?

Ques 47. Can javascript code be broken in different lines?

Ques 48. To put a "close window" link on a page?

Ques 49. How to hide javascript code from old browsers that dont run it?

Ques 50. How to comment javascript code?

Ques 51. Name the numeric constants representing max,min values?

Ques 52. What does javascript null mean?

Ques 53. How do you create a new object in JavaScript?

Ques 54. How do you assign object properties?

Ques 55. What’s a way to append a value to an array?

Ques 56. To set all checkboxes to true using JavaScript?

Ques 57. What is === operator?

Ques 58. How to disable an HTML object?

Ques 59. To write messages to the screen without using "document.write()"?

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