JavaScript

1. Java Script Module 2. World Wide Web (WWW) 3. Web Terms 4. NEED FOR SCRIPT 5. Introduction to Internet Programming 6. CLIENT SIDE and SERVER SIDE Scripting 7. Different Scripting Languages 8. Introduction to JavaScript 9. JavaScript and Security 10. How to Enable JavaScript 11. Advantages of Java Script 12. Limitations with JavaScript 13. Difference between JavaScript and JAVA 14. Difference between JavaScript and VBScript 15. JavaScript Development Tools 16. JavaScript Programming Techniques 17. JavaScript terms 18. Starting with JavaScript Programming step by step 19. Time to start JavaScript Programming 20. JavaScript Variables 21. JavaScript RESERVED WORDS 22. JavaScript Data Type 23. NUMBER DATA TYPE 24. BOOLEAN DATA TYPE 25. STRING DATA TYPE 26. NULL DATA TYPE 27. JavaScript Undefined DATA TYPE 28. JavaScript Operators 29. JavaScript Arithmetic Operators 30. JavaScript Logical Operators 31. JavaScript Comparison Operators 32. JavaScript String Operators 33. Bit Manipulation Operators 34. JavaScript Assignment Operators 35. JavaScript Conditional Operator 36. Conversion between JavaScript Data Types 37. Alert JavaScript function 38. confirm JavaScript function 39. prompt JavaScript function 40. JavaScript Statements 41. Single line & Multi-line Comments 42. JavaScrip If Statement 43. JavaScript if..else Statements 44. JavaScript If…else..if statement. 45. JavaScript For Statement 46. JavaScript For..in Statement: 47. JavaScript While Statement 48. JavaScript do while Statement: 49. JavaScript break and continue statement 50. JavaScript switch Statement: 51. JavaScript function() 52. JavaScript function with a Return Value 53. JavaScript with Statement 54. try, catch, and throw Statements 55. JavaScript ARRAY 56. JavaScript array of different data types 57. JavaScript ARRAY and Bubble sorting Program 58. JavaScript Array Methods 59. concate() method 60. every() method 61. filter() method 62. forEach() method 63. indexOf() method 64. Join() method 65. lastIndexOf() method 66. map() method 67. reduce() method 68. reduceRight() method 69. reverse() method 70. some() method 71. toSource() method 72. toString() method 73. pop() method 74. push() method 75. shift () method 76. slice () method 77. splice () method 78. sort() method 79. unshift() method 80. EVENT handling with JavaScript 81. onblur JavaScript Event 82. onchange JavaScript Event 83. onclick JavaScript Event 84. onDblClick JavaScript Event 85. onfocus JavaScript Event 86. onkeydown JavaScript Event 87. onkeyup JavaScript Event 88. Onkeypress JavaScript Event 89. onLoad JavaScript Event 90. onMousedown JavaScript Event 91. onMouseup JavaScript Event 92. Onmouseover JavaScript Event 93. onmouseout JavaScript Event 94. onMouseMove JavaScript Event 95. onReset JavaScript Event 96. onsubmit JavaScript Event 97. onUnload JavaScript Event 98. The Screen Object 99. JavaScript Interview Part1 100. JavaScript Interview Part2 101. JavaScript Interview Part3 102. JavaScript Interview Part4 103. JavaScript Interview Part5 104. JavaScript Interview Part6 105. JavaScript Interview Part7 106. JavaScript Interview Part8 107. JavaScript Interview Part9 108. JavaScript Interview Part10
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JavaScript Interview Questions and Answers Part 4

 

31. To put a "close window" link on a page ?

  • <a href='javascript:window.close()' class='mainnav'> Close </a>

 

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

  • Use the below specified style of comments <script language=javascript> <!-- javascript code goes here // --> or Use the <NOSCRIPT>some html code </NOSCRIPT> tags and code the display html statements between these and this will appear on the page if the browser does not support javascript

 

33. How to comment javascript code?

  • Comment is used to insert extra remarks in Script program. It can be used for specifying explaining logic of program, Purpose of Program or variable, Structure of program etc.

  • /* …… */ is used to write comments for more than one line. You can insert /* and */ and write more than one remarks.

  • While // comment is used to write single line remark. It can be placed even after any statements or command. As you can see in above program we have place remark after document.write

Example 1:

  • // this is a simple comment

  • You can place the // comment characters anywhere on a line.

  • JavaScript will treat all the text on that line after the // as a comment

Example 2:

  • MyVariable = “This is a test” // assigns text variable MyVariable

  • When writing long comments it's better to use the alternate commenting characters /* and */. Text between these characters is treated as a comment. Alternatively, you can start each line with the // comment characters.

Example 3:

  • // This section checks to see if the Enter key is pressed, // then continues on

 

34. Name the numeric constants representing max,min values

  • Number.MAX_VALUE

  • Number.MIN_VALUE

 

35. What does javascript null mean?

  • The null value is a unique value representing no value or no object.

  • It implies no object,or null string,no valid boolean value,no number and no array object.

 

36.To set all checkboxes to true using JavaScript?

//select all input tags

function SelectAll() {

var checkboxes = document.getElementsByTagName("input");

for(i=0;i<checkboxes.length;i++) {

if(checkboxes.item(i).attributes["type"].value == "checkbox") {

checkboxes.item(i).checked = true;

}

}

}

 

37. What does undefined value mean in javascript?

  • Undefined value means the variable used in the code doesn't exist or is not assigned any value or the property doesn't exist.

 

38. What is the difference between undefined value and null value?

 

Undefined value

Null value

Undefined value cannot be explicitly stated that is there is no keyword called undefined

Whereas null value has keyword called null

typeof undefined variable or property returns undefined

Whereas typeof null value returns object

39. What is variable typing in javascript?

  • It is perfectly legal to assign a number to a variable and then assign a string to the same variable as follows

example

i = 10;

i = "string";

  • This is called variable typing

 

40. Does javascript have the concept level scope?

  • No. JavaScript does not have block level scope, all the variables declared inside a function possess the same level of scope unlike c, c++, java.


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