js_tutorial

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Javascript Error Messages in Firefox or Mozilla Other browsers like Firefox, Netscape, and Mozilla send error messages to a special window called the JavaScript Console or Error Console. To view the console, select Tools --> Error Console or Web Development. Unfortunately, since these browsers give no visual indication when an error occurs, you must keep the Console open and watch for errors as your script executes. 368
Javascript Error Notifications Error notifications that show up on Console or through Internet Explorer dialog boxes are the result of both syntax and runtime errors. These error notification include the line number at which the error occurred. If you are using Firefox, then you can click on the error available in the error console to go to the exact line in the script having error. How to Debug a Script There are various ways to debug your JavaScript: Use a JavaScript Validator One way to check your JavaScript code for strange bugs is to run it through a program that checks it to make sure it is valid and that it follows the official syntax rules of the language. These programs are called validating parsers or just validators for short, and often come with commercial HTML and JavaScript editors. The most convenient validator for JavaScript is Douglas Crockford's JavaScript Lint, which is available for free at Douglas Crockford's JavaScript Lint. Simply visit that web page, paste your JavaScript (Only JavaScript) code into the text area provided, and click the <strong>js</strong>lint button. This program will parse through your JavaScript code, ensuring that all the variable and function definitions follow the correct syntax. It will also check JavaScript statements, such as if and while, to ensure they too follow the correct format Add Debugging Code to Your Programs You can use the alert() or document.write() methods in your program to debug your code. For example, you might write something as follows: ar debugging = true; var whichImage = "widget"; if( debugging ) alert( "Calls swapImage() with argument: " + whichImage ); var swapStatus = swapImage( whichImage ); if( debugging ) alert( "Exits swapImage() with swapStatus=" + swapStatus ); By examining the content and order of the alert() as they appear, you can examine the health of your program very easily. 369
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About the Tutorial JavaScript is a
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Bitwise Operators .................
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23. String ........................
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setUTCDate () .....................
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Checking for Plug-Ins .............
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1. OVERVIEW Javascript What is Java
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Javascript components, integrates w
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Javascript This function can be use
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Javascript The following example sh
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Javascript JavaScript in Chrome Her
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4. PLACEMENT Javascript There is a
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Javascript This code will
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5. VARIABLES Javascript JavaScript
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Javascript Within the body of a fun
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6. OPERATORS Javascript What is an
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Javascript document.write("a - b =
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Javascript the right operand, if ye
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Javascript Output (a == b) => false
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Javascript Output (a && b) => fal
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Javascript document.write("(a | b)
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Javascript Ex: C /= A is equivalent
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Javascript Set the variables to dif
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Javascript Function Undefined Null
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7. IF-ELSE Javascript While writing
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Javascript Output Qualifies for dri
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Javascript Try the following code t
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Javascript Syntax The objective of
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Javascript switch (grade) { case 'A
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Javascript Syntax The syntax of whi
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Javascript do{ Statement(s) to be e
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10. FOR LOOP Javascript The for Loo
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Javascript Current Count : 6 Curren
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Javascript Set the variable to diff
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Javascript Set the variable to
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Javascript Entering the loop 2 3 4
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Javascript Output Entering th
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13. FUNCTIONS Javascript A function
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Javascript Click the following butt
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Javascript Click the following but
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Javascript Use different parameters
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Javascript var variablename = funct
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14. EVENTS Javascript What is an Ev
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Javascript ....... onmouseove
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Javascript ondragenter script Trigg
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Javascript onplaying script Trigger
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15. COOKIES Javascript What are Coo
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Javascript Enter name: Outp
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Javascript Setting Cookies Expiry D
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Javascript Output Enter Cookie Na
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Javascript Example Try the followin
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Javascript setTimeout('Redirect()',
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17. DIALOG BOX Javascript JavaScrip
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Javascript Output Click the fol
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18. VOID KEYWORD Javascript void is
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Javascript Click the followin
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Javascript 2. If you do not want to
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Javascript 104
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Javascript Methods are useful for e
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Javascript Output Book title is
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Javascript User-defined objects /
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Javascript In the following section
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Javascript Click the following t
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Javascript Day of the Month must be
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Javascript alert("Value of bigNumbe
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Javascript constructor It returns a
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Javascript Try the following exampl
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Javascript document.write(""); docu
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Javascript document.write("num.toPr
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Javascript Returns the primitive va
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Javascript Returns the function tha
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Javascript Method toSource() toStri
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Javascript Output flag.toString
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23. STRING Javascript The String ob
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Javascript concat() indexOf() lastI
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Javascript document.writeln("str.ch
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Javascript Argument Details string2
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Javascript lastIndexOf () This meth
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Javascript var index = str1.localeC
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Javascript substring. $n or $nn Whe
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Javascript Search () This method ex
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Javascript document.write( sliced )
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Javascript Return Value Returns a s
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Javascript JavaScript String toLow
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Javascript var str = "Apples are r
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Javascript were in a tag sup() Cau
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Javascript blink () This method cau
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Javascript JavaScript String font
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Javascript JavaScript String link(
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Javascript JavaScript String strik
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Javascript JavaScript String sup(
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Javascript input length prototype T
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Javascript Prototype The prototype
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Javascript push() reduce() reduceRi
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Javascript every () Javascript arra
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Javascript } var passed = [12, 5, 8
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Javascript Array.prototype.filter =
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Javascript } }; Example Try the fol
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Javascript var len = this.length; v
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Javascript join () Javascript array
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Javascript var from = Number(argume
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Javascript } var index = [12, 5, 8,
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Javascript Array.prototype.map = fu
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Javascript Its syntax is as follows
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Javascript var rv = arguments[1]; }
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Javascript } } throw new TypeError(
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Javascript } rv = this[i--]; break;
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Javascript } rv = fun.call(null, rv
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Javascript Output Removed element
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Javascript { } if (i in this && fun
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Javascript Return Value Returns a s
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Javascript toString () Javascript a
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25. DATE Javascript The Date object
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Javascript Return Value Returns the
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Javascript Date Methods Here is a l
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Javascript universal time. setUTCMo
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Javascript Syntax Its syntax is as
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Javascript var dt = new Date(); d
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Javascript getMonth() : 11 getSecon
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Javascript Output getUTCHours() :
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Javascript JavaScript getYear Met
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Javascript JavaScript setFullYear
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Javascript If you specify a number
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Javascript monthValue : An integ
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Javascript setTime () Javascript da
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Javascript Date.setUTCFullYear(year
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Javascript document.write( dt );
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Javascript var dt = new Date(1993,
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Javascript toLocaleDateString () Ja
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Javascript For instances of Date,
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Javascript var dateobject = new
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Javascript Output 743850547000 Date
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Javascript minutes : An integer
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Javascript In the following section
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Javascript Property Value is : 0.43
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Javascript JavaScript Math SQRT2 P
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Javascript First Test Value : 3.141
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Javascript JavaScript Math atan() M
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Javascript var value = Math.atan2(+
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Javascript Output First Test Value
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Javascript var value = Math.log(10
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Javascript min ( ) This method retu
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Javascript var value = Math.pow(7,
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Javascript Return Value Returns the
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Javascript Output First Test Val
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27. REGEXP Javascript A regular exp
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Javascript Examples Following examp
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Javascript m g Specifies that if th
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Javascript Test1 - ignoreCase prope
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Page 330 and 331: Javascript exec ( ) The exec method
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Page 354 and 355: Javascript Logical Errors Logic err
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Page 362 and 363: 30. FORM VALIDATION Javascript Form
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Page 366 and 367: Javascript var emailID = document.m
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Page 370 and 371: Javascript } function moveRight(){
Page 372 and 373: Javascript It is not possible to s
Page 374 and 375: Javascript Output Checking for Plug
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Page 382 and 383: 34. IMAGE MAP Javascript You can us
Page 384 and 385: Javascript Output You can feel the
Page 386 and 387: Javascript 6 plugins[] This propert
Page 388: Javascript document.write(" Browser
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