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Top 100+ Java Script Interview Questions And Answers

Question 1. What Is Javascript?

Answer :

JavaScript is a trendy-motive programming language designed to allow programmers of all skill tiers manage the conduct of software items. The language is used maximum extensively today in Web browsers whose software program objects have a tendency to represent a variety of HTML factors in a file and the document itself. But the language can be--and is--used with different types of gadgets in different environments. For example, Adobe Acrobat Forms makes use of JavaScript as its underlying scripting language to glue together items which might be specific to the paperwork generated by Adobe Acrobat. Therefore, it's miles critical to distinguish JavaScript, the language, from the items it could communicate with in any precise surroundings. When used for Web files, the scripts cross directly within the HTML documents and are downloaded to the browser with the rest of the HTML tags and content material.

JavaScript is a platform-unbiased,event-pushed, interpreted customer-aspect scripting and programming language evolved by Netscape Communications Corp. And Sun Microsystems.

Question 2. How To Read And Write A File Using Javascript?

Answer :

I/O operations like analyzing or writing a document is not feasible with patron-facet javascript. However , this could be executed by way of coding a Java applet that reads files for the script.

Adv Java Interview Questions
Question three. What Are Javascript Types?

Answer :

Number, String, Boolean, Function, Object, Null, Undefined.

Question 4. How Do You Convert Numbers Between Different Bases In Javascript?

Answer :

Use the parseInt() function, that takes a string as the first parameter, and the bottom as a 2d parameter. So to convert hexadecimal 3F to decimal, use parseInt ("3F", 16);

Java Script Tutorial
Question five. What Can Javascript Programs Do?

Answer :

Generation of HTML pages on-the-fly without accessing the Web server. The user may be given manage over the browser like User input validation Simple computations may be finished at the purchaser's gadget The user's browser, OS, display length, and so on. May be detected Date and Time Handling.

Core Java Interview Questions
Question 6. What Is The Data Type Of Variables Of In Javascript?

Answer :

All variables are of item kind in JavaScript.

Question 7. Is A Javascript Faster Than An Asp Script?

Answer :

Yes.Since javascript is a patron-aspect script it does require the web server's assist for its computation,so it is continually quicker than any server-side script like ASP,PHP,etc..

Adv Java Tutorial Java-Springs Interview Questions
Question eight. Are Java And Javascript The Same?

Answer :

No.Java and javascript are two extraordinary languages.
Java is a powerful item - oriented programming language like C++,C while Javascript is a client-side scripting language with a few barriers.

Question nine. How To Embed Javascript In A Web Page?

Answer :

javascript code may be embedded in a web page between <script langugage="javascript"></script> tags

Java Servlets Interview Questions
Question 10. How Is Javascript Different From Java?

Answer :

JavaScript became evolved by Brendan Eich of Netscape; Java changed into developed at Sun Microsystems. While the 2 languages share a few commonplace syntax, they were advanced independently of each different and for special audiences. Java is a full-fledged programming language tailor-made for community computing; it includes loads of its own objects, together with objects for creating user interfaces that appear in Java applets (in Web browsers) or standalone Java applications. In evaluation, JavaScript is predicated on anything environment it's running in for the person interface, together with a Web record's shape factors.

JavaScript changed into to begin with called LiveScript at Netscape while it changed into beneath improvement. A licensing deal between Netscape and Sun on the final minute allow Netscape plug the "Java" call into the call of its scripting language. Programmers use absolutely different gear for Java and JavaScript. It is also no longer unusual for a programmer of 1 language to be blind to the other. The languages do not depend on every other and are supposed for exclusive functions. In a few methods, the "Java" call on JavaScript has burdened the sector's understanding of the differences between the 2. On the alternative hand, JavaScript is lots simpler to learn than Java and might provide a gentle introduction for beginners who need to graduate to Java and the styles of packages you can expand with it.

Core Java Tutorial
Question eleven. What's Relationship Between Javascript And Ecmascript?

Answer :

ECMAScript is yet some other name for JavaScript (different names encompass LiveScript). The contemporary JavaScript which you see supported in browsers is ECMAScript revision three.

EJB(Enterprise JavaBeans) Interview Questions
Question 12. How Do You Submit A Form Using Javascript?

Answer :

Use report.Paperwork[0].Post();
(zero refers to the index of the shape – when you have multiple form in a page, then the primary one has the index 0, 2nd has index 1 and so forth).

Adv Java Interview Questions
Question thirteen. How To Detect The Operating System On The Client Machine?

Answer :

In order to hit upon the operating device at the patron gadget, the navigator.AppVersion string (belongings) have to be used.

Java-Springs Tutorial
Question 14. 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?

Answer :

JavaScript's greatest potential gift to a Web web site is that scripts can make the page greater straight away interactive, that is, interactive without having to put up every little component to the server for a server application to re-render the web page and send it lower back to the patron. For instance, consider a top-level navigation panel that has, say, six number one photograph map hyperlinks into subsections of the Web site. With simplest a bit bit of scripting, each map area may be advised to pop up a more precise list of hyperlinks to the contents inside a subsection each time the user rolls the cursor atop a map area. With the assist of that popup listing of links, the consumer with a scriptable browser can bypass one intermediate menu web page. The consumer without a scriptable browser (or who has disabled JavaScript) will ought to drill down through a more conventional and time-eating course to the preferred content.

Question 15. How To Create Arrays In Javascript?

Answer :

We can claim an array like this
var scripts = new Array();
We can add elements to this array like this

scripts[0] = "PHP";
scripts[1] = "ASP";
scripts[2] = "JavaScript";
scripts[3] = "HTML";

Now our array scrips has 4 elements inside it and we can print or get admission to them via the usage of their index quantity. Note that index wide variety starts offevolved from 0. To get the 1/3 element of the array we have to use the index number 2 . Here is the way to get the third element of an array.
File.Write(scripts[2]);
We can also create an array like this
var no_array = new Array(21, 22, 23, 24, 25);

JavaServer Faces (JSF) Interview Questions
Question 16. How Do You Target A Specific Frame From A Hyperlink?

Answer :

Include the call of the frame in the target characteristic of the hyperlink. <a href=”mypage.Htm” target=”myframe”>>My Page</a>

Java Servlets Tutorial
Question 17. What Is A Fixed-width Table And Its Advantages?

Answer :

Fixed width tables are rendered with the aid of the browser based at the widths of the columns inside the first row, ensuing in a quicker show in case of large tables. Use the CSS style table-layout:constant to specify a fixed width table.
If the desk is not unique to be of fixed width, the browser has to attend until all statistics is downloaded and then infer the nice width for each of the columns. This procedure may be very slow for massive tables.

Java Swing Interview Questions
Question 18. Example Of Using Regular Expressions For Syntax Checking In Javascript

Answer :

var re = new RegExp("^(&[A-Za-z_0-9]1,=[A-Za-z_0-9]1,)*$");
var textual content = myWidget.Fee;
var OK = re.Test(text);
if( ! OK )
alert("The more parameters need some work.Rn Should be some thing like: "&a=1&c=4"");

Core Java Interview Questions
Question 19. How To Add Buttons In Javascript?

Answer :

The most basic and historical use of buttons are the "put up" and "clear", which appear barely before the Pleistocene duration. Notice whilst the "GO!" button is pressed it submits itself to itself and appends the call in the URL.
<form action="" name="buttonsGalore" method="get">
Your Name: <input type="text" name="mytext" />
<br />
<input type="submit" value="GO!" />
<input type="reset" value="Clear All" />
</form>

Another beneficial method is to set the "kind" to "button" and use the "onclick" occasion.
<script type="text/javascript">
characteristic displayHero(button)
alert("Your hero is ""+button.Price+"".");

</script>

<form action="" name="buttonsGalore" method="get">
<fieldset style="margin: 1em; text-align: center;">
<legend>Select a Hero</legend>
<input type="button" value="Agamemnon" onclick="displayHero(this)" />
<input type="button" value="Achilles" onclick="displayHero(this)" />
<input type="button" value="Hector" onclick="displayHero(this)" />
<div style="height: 1em;" />
</fieldset>
</form>

EJB(Enterprise JavaBeans) Tutorial
Question 20. How To Set A Html Document's Background Color?

Answer :

record.Bgcolor assets can be set to any appropriate color.

Java Interview Questions
Question 21. How Can Javascript Be Used To Personalize Or Tailor A Web Site To Fit Individual Users?

Answer :

JavaScript allows a Web web page to carry out "if-then" kinds of choices based totally on browser model, operating system, consumer enter, and, in extra recent browsers, information about the display screen size wherein the browser is going for walks. While a server CGI software could make some of those equal kinds of choices, now not all people has get right of entry to to or the know-how to create CGI programs. For example, an experienced CGI programmer can study facts approximately the browser whenever a request for a page is made; thus a server so ready might serve up one page for Navigator users and a distinct page for Internet Explorer customers. Beyond browser and operating gadget version, a CGI program cannot understand greater about the environment. But a JavaScript-more desirable web page can train the browser to render simplest positive content material primarily based at the browser, running device, or even the display screen length.

Scripting may even cross similarly if the page writer dreams. For instance, the author can also encompass a preference display that shall we the consumer decide the desired history and textual content colour mixture. A script can store this facts at the purchaser in a well-regulated neighborhood document called a cookie. The next time the user involves the site, scripts in its pages look to the cookie information and render the web page within the shade aggregate decided on previously. The server is none the wiser, nor does it ought to save any visitor-specific facts.

Question 22. Are You Concerned That Older Browsers Don't Support Javascript And Thus Exclude A Set Of Web Users? Individual Users?

Answer :

Fragmentation of the set up base of browsers will most effective worsen. By definition, it can by no means enhance except truely everybody on this planet threw away their old browsers and upgraded to the cutting-edge gee-whiz versions. But even then, there are plenty of discrepancies between the scriptability of the state-of-the-art Netscape Navigator and Microsoft Internet Explorer.

The situation makes scripting a undertaking, mainly for learners who might not be privy to the restrictions of earlier browsers. A lot of attempt in my books and ancillary cloth is going in the direction of helping scripters recognise what functions work wherein browsers and the way to either workaround obstacles in in advance browsers or raise the compatibility common denominator.

Designing scripts for a Web site calls for making a few difficult selections about if, when, and a way to implement the blessings scripting gives a page for your target audience. For public Web websites, I recommend the usage of scripting in an additive manner: let sufficient content stand on its very own, but let scriptable browser users receive an greater experience, preferably with the identical HTML document.

JavaServer Faces (JSF) Tutorial
Question 23. What Does Isnan Function Do?

Answer :

Return true if the argument isn't always a range of.

Javascript Objects Interview Questions
Question 24. What Is Negative Infinity?

Answer :

It’s a number of in JavaScript, derived by using dividing negative quantity by means of zero.

Java-Springs Interview Questions
Question 25. In A Pop-up Browser Window, How Do You Refer To The Main Browser Window That Opened It?

Answer :

Use window.Opener to consult the main window from pop-ups.

Java Swing Tutorial
Question 26. Methods Get And Post In Html Forms - What's The Difference?.

Answer :

GET: Parameters are passed within the querystring. Maximum amount of records that may be despatched via the GET technique is constrained to about 2kb.

POST: Parameters are surpassed in the request frame. There is not any restrict to the amount of statistics that may be transferred the use of POST. However, there are limits at the maximum amount of information that can be transferred in a single call/value pair.

Javascript Advanced Interview Questions
Question 27. How To Write A Script For "pick" Lists Using Javascript

Answer :

1. To put off an item from a listing set it to null
mySelectObject.Options[3] = null;
2. To truncate a listing set its length to the maximum size you preference
mySelectObject.Duration = 2;
3. To delete all alternatives in a pick out object set the period to zero.
MySelectObject.Leng

Java Servlets Interview Questions
Question 28. Text From Your Clipboard?

Answer :

It is genuine, textual content you ultimate copied for pasting (replica & paste) can be stolen while you visit web web sites using a combination of JavaScript and ASP (or PHP, or CGI) to write your viable sensitive records to a database on any other server.

Java Tutorial
Question 29. What Does The "access Is Denied" Ie Error Mean?

Answer :

The "Access Denied" blunders in any browser is due to the subsequent cause.
A javascript in one window or body is tries to get entry to another window or body whose file's domain is different from the file containing the script.

JavaMail API Interview Questions
Question 30. What Are The Problems Associated With Using Javascript, And Are There Javascript Techniques That You Discourage?

Answer :

Browser version incompatibility is the most important hassle. It requires understanding how each scriptable browser version implements its item version. You see, the incompatibility rarely has to do with the core JavaScript language (even though there had been enhancements to the language over the years); the majority of incompatibility troubles must do with the object models that every browser version implements. For example, scripters who started out with Navigator three carried out the photograph rollover as it looked cool. But they had been dismayed to find out that the photograph item wasn't scriptable in Internet Explorer three or Navigator 2. While there are clean workarounds to make this feature work on newer browsers without worrying older ones, it became a painful getting to know revel in for plenty.

The 2nd largest can of worms is scripting connections among more than one windows. A lot of scripters want to have little home windows pop up with navigation bars or some such gizmos. But the item fashions, especially inside the older browser variations, don't make it easy to work with these home windows the minute you put a user in front of them--users who can manually near home windows or alternate their stacking order. More lately, a glitch in a few uninstall routines for Windows ninety five programs can disturb essential components of the machine Registry that Internet Explorer four requires for coping with a couple of home windows. A scripter can't work round this hassle, as it's not feasible to stumble on the hassle in a user's system. I tend to avoid more than one windows that interact with every different. I suppose a whole lot of inexperienced Web surfers can also get burdened by4 Evaluate To?

Answer :

Since 1 is a string, the whole lot is a string, so the result is 124.

Java 8 Interview Questions
Question 33. What Are The Ways To Emit Client-side Javascript From Server-side Code In Asp.Net?

Answer :

The Page item in ASP.NET has strategies that permit emitting of purchaser-side JavaScript:
RegisterClientScriptBlock and RegisterStartupScript.
Example usage:

Page.RegisterClientScriptBlock("ScriptKey", "<script language=javascript>" + "feature TestFn() alert('Clients-aspect JavaScript'); </script>");
Page.RegisterStartupScript("ScriptKey", "<script language=javascript>" + "function TestFn() alert('Clients-facet JavaScript'); </script>");

ScriptKey is used to suppress the same JavaScript from being emitted extra than as soon as. Multiple calls to RegisterClientScriptBlock or RegisterStartupScript with the same value of ScriptKey emit the script best once, on the first name.

EJB(Enterprise JavaBeans) Interview Questions
Question 34. What Is The Difference Between Registerclientscriptblock And Registerstartupscript?

Answer :

RegisterClientScriptBlock emits the JavaScript simply after the hole tag. RegisterStartupScript emits the JavaScript at the lowest of the ASP.NET web page just earlier than the ultimate tag.

Question 35. What Is The Difference Between A Web-garden And A Web-farm?

Answer :

Web-garden - An IIS6.0 feature wherein you may configure an software pool as an internet-lawn and additionally specify the variety of employee processes for that pool. It can assist improve overall performance in some cases.

Web-farm - a preferred time period regarding a cluster of physically separate machines, each strolling a web-server for scalability and overall performance (evaluation this with web-lawn which refers to multiple methods on one single physical device).

Question 36. How To Get The Contents Of An Input Box Using Javascript?

Answer :

Use the "price" assets.
Var myValue = window.Document.GetElementById("MyTextBox").Cost;

JavaServer Faces (JSF) Interview Questions
Question 37. How To Determine The State Of A Checkbox Using Javascript?

Answer :

var checkedP = window.Document.GetElementById("myCheckBox").Checked;

Question 38. How To Set The Focus In An Element Using Javascript?

Answer :

Question 39. How To Access An External Javascript File That Is Stored Externally And Not Embedded?

Answer :

This may be performed via the use of the subsequent tag between head tags or among frame tags.
<script src="abc.Js"></script>How to get entry to an external javascript report that is stored externally and not embedded? Wherein abc.Js is the outside javscript file to be accessed.

Question forty. What Is The Difference Between An Alert Box And A Confirmation Box?

Answer :

An alert container presentations most effective one button that's the OK button while the Confirm field displays two buttons namely OK and cancel.

Java Swing Interview Questions
Question 41. What Is A Prompt Box?

Answer :

A set off field permits the person to enter input by offering a text field.

Question 42. Can Javascript Code Be Broken In Different Lines?

Answer :

Breaking is possible inside a string announcement by means of using a backslash at the stop however not within another javascript statement.
This is ,
report.Write("Hello international");
is feasible but not document.Write
("hi there international");

Java Interview Questions
Question forty three. Taking A Developer's Perspective, Do You Think That That Javascript Is Easy To Learn And Use?

Answer :

One of the motives JavaScript has the word "script" in it's far that as a programming language, the vocabulary of the middle language is compact as compared to full-fledged programming languages. If you already application in Java or C, you clearly ought to unlearn some concepts that had been overwhelmed into you. For instance, JavaScript is a loosely typed language, which means that a variable does not care if it is keeping a string, a number, or a connection with an item; the same variable can even exchange what form of facts it holds while a script runs.

The different part of JavaScript implementation in browsers that makes it less complicated to examine is that most of the items you script are pre-described for the author, and that they largely constitute physical matters you could see on a page: a textual content box, an picture, and so forth. It's less difficult to mention, "OK, these are the matters I'm operating with and I'll use scripting to cause them to do such and such," rather of getting to dream up the person interface, conceive of and code gadgets, and manage the interaction between items and customers. With scripting, you generally tend to jot down a _lot_ much less code.

Question forty four. How About 2+5+"8"?

Answer :

Since 2 and 5 are integers, that is wide variety mathematics, in view that eight is a string, it’s concatenation, so seventy eight is the end result.

Question forty five. What Is The Difference Between Sessionstate And Viewstate?

Answer :

ViewState is particular to a page in a session. Session country refers to consumer particular statistics that can be accessed throughout all pages in the web application.

Question forty six. What Does The Enableviewstatemac Setting In An Aspx Page Do?

Answer :

Setting EnableViewStateMac=authentic is a safety measure that lets in ASP.NET to make sure that the viewstate for a page has not been tampered with. If on Postback, the ASP.NET framework detects that there has been a change within the cost of viewstate that changed into sent to the browser, it raises an blunders - Validation of viewstate MAC failed.

Use <%@ Page EnableViewStateMac="true"%> to set it to true (the default cost, if this attribute isn't precise is also authentic) in an aspx page.

Question forty seven. How To Accessing Elements Using Javascript?

Answer :

To do some thing exciting with HTML elements, we should first be capable of uniquely perceive which detail we need. In the instance
<body>
<form action="">
<input type="button" id="useless" name="mybutton" value="doNothing" />
</form>
</body>

We can use the "getElementById" technique (that's typically favored)
file.GetElementById("useless").Fashion.Coloration = "red";
or we will use the older hierarchical navigation method,
report.Forms[0].Mybutton.Fashion.Colour = "blue";
Notice that this makes use of the "name" characteristic of the element to discover it.
# Example of Accessing Elements in a DOM.

</script>

<form name="beerForm" action="">
<select name="beer">
<option selected="selected">Select Beer</option>
<option>Heineken</option>
<option>Amstel Light</option>
<option>Corona</option>
<option>Corona Light</option>
<option>Tecate</option>
</select>

Question 48. What Looping Structures Are There In Javascript?

Answer :

for, even as, do-whilst loops, but no foreach.

Question forty nine. To Put A "close Window" Link On A Page ?

Answer :

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

Question 50. How To Hide Javascript Code From Old Browsers That Dont Run It?

Answer :

Use the under targeted fashion of remarks <script language=javascript>  or Use the <NOSCRIPT>a few html code </NOSCRIPT> tags and code the display html statements between those and this may seem on the page if the browser does now not guide javascript

Question fifty one. How To Comment Javascript Code?

Answer :

Use // for line remarks and
/*

*/ for block remarks

Question fifty two. Name The Numeric Constants Representing Max,min Values

Answer :

Number.MAX_VALUE
Number.MIN_VALUE

Question fifty three. What Does Javascript Null Mean?

Answer :

The null value is a completely unique cost representing no value or no item. It implies no object,or null string,no legitimate boolean value,no number and no array item.

Question 54. How Do You Create A New Object In Javascript?

Answer :

var obj = new Object(); or var obj = ;

Question fifty five. How Do You Assign Object Properties?

Answer :

obj["age"] = 17 or obj.Age = 17.

Question 56. What Is This Keyword?

Answer :

It refers to the present day item.

Question 57. What Does The Term Sticky Session Mean In A Web-farm Scenario? Why Would You Use A Sticky Session? What Is The Potential Disadvantage Of Using A Sticky Session?

Answer :

Sticky consultation refers to the feature of many commercial load balancing solutions for net-farms to course the requests for a selected session to the equal bodily device that serviced the primary request for that session. This is specifically used to ensure that a in-proc consultation is not lost due to requests for a session being routed to different servers. Since requests for a user are constantly routed to the identical device that first served the request for that session, sticky sessions can reason choppy load distribution throughout servers.

Question fifty eight. You Have An Asp.Internet Web Application Running On A Web-farm That Does Not Use Sticky Sessions - So The Requests For A Session Are Not Guaranteed To Be Served The Same Machine. Occasionally, The Users Get Error Message Validation Of Viewstate Mac Failed. What Could Be One Reason That Is Causing This Error?

Answer :

The maximum commonplace cause for this error is that the the machinekey cost in machine.Config is special for each server. As a result, viewstate encoded through one system can't be decoded by way of some other. To rectify this, edit the device.Config record on every server in the web-farm to have the same cost for machinekey.

Question fifty nine. To Set All Checkboxes To True Using Javascript?

Answer :

//choose all enter 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 = genuine;

Question 60. How To Select An Element By Id And Swapping An Image ?

Answer :

</script>
<img border="0" src="" id="brandIcon" alt="brand" />
<select name="beer" id="beer" onChange="setButton();setBeerIcon();">
<option value="--Select--">Select beer</option>
<option value="heineken">heineken</option>
<option value="sol">sol</option>
<option value="amstellight">amstellight</option>
<option value="coronalight">coronalight</option>
<option value="coronaextra">coronaextra</option>
<option value=""></option>
</select>

Question sixty one. What Does Undefined Value Mean In Javascript?

Answer :

Undefined cost way the variable used in the code doesnt exist or isn't always assigned any fee or the property doesnt exist.

Question sixty two. What Is The Difference Between Undefined Value And Null Value?

Answer :

(i)Undefined value cannot be explicitly stated this is there may be no keyword referred to as undefined whereas null value has keyword referred to as null
(ii)typeof undefined variable or assets returns undefined while typeof null cost returns item

Question 63. What Is Variable Typing In Javascript?

Answer :

It is perfectly criminal 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

Question 64. Does Javascript Have The Concept Level Scope?

Answer :

No.Javascript does not have block degree scope,all of the variables declared interior a feature possess the identical degree of scope unlike c,c++,java.

Question 65. What Are Undefined And Undeclared Variables?

Answer :

Undeclared variables are those that aren't declared inside the software (do now not exist in any respect),trying to study their values gives runtime blunders.But if undeclared variables are assigned then implicit declaration is carried out .

Undefined variables are those who are not assigned any value but are declared within the software.Trying to read such variables gives special value known as undefined value.

Question 66. What Is === Operator ?

Answer :

==== is strict equality operator ,it returns true best whilst the 2 operands are having the same price with none kind conversion.

Question sixty seven. How To Find The Selected Radio Button Immediately Using The 'this' Variable?

Answer :

</script>
<input type="radio" name="marsupial" value="kangaroo"
onchange="favAnimal(this)">Kangaroo
<br /><input type="radio" name="marsupial" value="Opossum"
onchange="favAnimal(this)">Opossum
<br /><input type="radio" name="marsupial" value="Tasmanian Tiger"
onchange="favAnimal(this)">Tasmanian Tiger

Question sixty eight. How To Find Radio Button Selection When A Form Is Submitted?

Answer :

alert("You selected ""+myForm.Marsupial[i].Fee+"".");

</script>
<form name="animalForm" action="">
<input type="radio" name="marsupial" value="kangaroo" />Kangaroo
<br /><input type="radio" name="marsupial" value="Opossum" />Opossum
<br /><input type="radio" name="marsupial" value="Tasmanian Tiger" />Tasmanian Tiger
<input type="button" name="GO" value="GO" onclick="findButton()" />

Question 69. How To Disable An Html Object

Answer :

record.GetElementById("myObject").Disabled = authentic;

Question 70. To Write Messages To The Screen Without Using "document.Write()" ?

Answer :

Changing the contents of an detail is a far better solution. When the method showStatus is invoked it's going to alternate the content material of the span.
...
Feature showStatus(message)
var element = report.GetElementById("mystatus");
element.TextContent = message; //for Firefox
element.InnerHTML = message; //for IE (why cannot we all just get alongside?)
return genuine;

...
<span id="mystatus">Test. </span>

Question seventy one. How To Add New Elements Dynamically.

Answer :

<html xmlns="http://www.W3.Org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>t1</title>
<script type="text/javascript">
feature addNode()
var newP = report.CreateElement("p");
var textNode = document.CreateTextNode(" I'm a brand new textual content node");
newP.AppendChild(textNode);
file.GetElementById("firstP").AppendChild(newP);

</script>
</head>
<body onload="addNode();" style=" background: url('../images/Sand-1280.Jpg'); background-color: yellow;">
<p id="firstP">firstP<p>
</body>
</html>

Question seventy two. How To Have An Element Invoke A Javascript On Selection, Instead Of Going To A New Url:

Answer :

</script>
<a href="javascript:pseudoHitMe()">hit me</a>

Question seventy three. How To Have The Status Line Update When The Mouse Goes Over A Link (the Support Of The Status Line Is Sporadic)?

Answer :

<a href="javascript.Shtml"
onmouseover="window.Status='Hi There!';return true"
onmouseout="window.Status='';return true">Look on the Status bar</a>
Look at the Status bar as your cursor is going over the link.

Question 74. How To Create A Popup Warning Box

Answer :

alert('Warning: Please enter an integer between 0 and 100.');

Question seventy five. How To Create A Confirmation Box?

Answer :

affirm("Do you actually need to release the missile?");

Question seventy six. How To Create An Input Box?

Answer :

prompt("What is your temperature?");

Question 77. How To Open A Window With No Toolbar, But With The Location Object.

Answer :

window.Open("http://www.Mysite.Org/Misc/Pennies","Pennies","resizable=yes, reputation=sure,toolbar=yes,place=yes,menubar=sure,scrollbars=sure,width=800,peak=400");

Question seventy eight. How To Setting A Cookie With The Contents Of A Textbox ?

Answer :

Values stored in cookies won't have semicolons, commas, or spaces. You should use the handy "escape()" characteristic to encode the values, and "unescape()" to retrieve them.

//Sets cookie of contemporary cost for myTextBox
feature TextBoxOnchange()
var myBox = window.Report.GetElementById(myTextBox");
report.Cookie = "myTextBox="+ get away(myBox.Value) + getExpirationString();

//return a string like ";expires=Thu, 5 Jan 2006 sixteen:07:fifty two UTC"
function getExpirationString()
var exp = new Date();
var threemonths = exp.GetTime()+(120*24*60*60*one thousand);
exp.SetTime(threemonths);
go back ";expires="+exp.ToGMTString();

This is known as from the occasion handler within the HTML.

Question seventy nine. How To Getting Values From Cookies To Set Widgets?

Answer :

characteristic getCookieData(labelName)
//from Danny Goodman
var labelLen = labelName.Length;
// read cookie belongings best once for velocity
var cookieData = report.Cookie;
var cLen = cookieData.Duration;
var i = 0;
var cEnd;
even as (i < cLen)
var j = i + labelLen;
if (cookieData.Substring(i,j) == labelName)
cEnd = cookieData.IndexOf(";",j);
if (cEnd == -1)
cEnd = cookieData.Period;

return unescape(cookieData.Substring(j+1, cEnd));

i++;

go back "";

//init() is known as from the body tag onload function.
Characteristic init()
setValueFromCookie("brand");
setValueFromCookie("market");
setValueFromCookie("degree");

characteristic setValueFromCookie(widget)
if( getCookieData(widget) != "")
record.GetElementById(widget).Cost = getCookieData(widget);

//if you name your cookies the widget ID, you may use the following helper function
function setCookie(widget)
report.Cookie = widget + "=" +
break out(record.GetElementById(widget).Fee) + getExpirationString();

Question 80. How To Change Style On An Element?

Answer :

Between CSS and javascript is a peculiar symmetry. CSS fashion guidelines are layed on pinnacle of the DOM. The CSS property names like "font-weight" are transliterated into "myElement.Style.FontWeight". The elegance of an detail can be swapped out. For instance:
file.GetElementById("myText").Fashion.Color = "inexperienced";
report.GetElementById("myText").Fashion.FontSize = "20";
-or-
report.GetElementById("myText").ClassName = "ordinary";

Question 81. How To Make Elements Invisible

Answer :

Change the "visibility" characteristic of the style item associated with your detail. Remember that a hidden detail still takes up space, use "display" to make the space disappear as well.

If ( x == y)
myElement.Style.Visibility = 'seen';
else
myElement.Style.Visibility = 'hidden';

Question eighty two. How To Set The Cursor To Wait.

Answer :

In principle, we should cache the present day kingdom of the cursor after which put it again to its unique kingdom.
Document.Frame.Fashion.Cursor = 'wait';
//do something thrilling and time consuming
document.Body.Fashion.Cursor = 'auto';

Question 83. How To Reload The Current Page

Answer :

window.Area.Reload(genuine);

Question eighty four. How To Force A Page To Go To Another Page Using Javascript?

Answer :

Question eighty five. How To Convert A String To A Number Using Javascript?

Answer :

You can use the parseInt() and parseFloat() techniques. Notice that extra letters following a legitimate wide variety are neglected, that's kinda wierd but convenient at times.
ParseInt("a hundred") ==> 100
parseFloat("98.6") ==> ninety eight.6
parseFloat("98.6 is a common temperature.") ==> ninety eight.6
parseInt("aa") ==> Nan //Not a Number
parseInt("aa",sixteen) ==> one hundred seventy //you can deliver a radix or base

Question 86. How To Convert Numbers To Strings Using Javascript?

Answer :

You can prepend the quantity with an empty string
var mystring = ""+myinteger;
or
var mystring = myinteger.ToString();
You can specify a base for the conversion,
var myinteger = 14;
var mystring = myinteger.ToString(16);
mystring will be "e".

Question 87. How To Test For Bad Numbers Using Javascript?

Answer :

the global technique, "isNaN()" can tell if a range of has gone bad.
Var temperature = parseFloat(myTemperatureWidget.Cost);
if(!IsNaN(temperature))
alert("Please input a legitimate temperature.");

Question 88. What's Math Constants And Functions Using Javascript?

Answer :

The Math object includes beneficial constants inclusive of Math.PI, Math.E
Math also has a zillion beneficial functions.
Math.Abs(value); //absolute fee
Math.Max(value1, value2); //locate the most important
Math.Random() //generate a decimal range between zero and 1
Math.Floor(Math.Random()*one hundred and one) //generate a decimal variety between 0 and a hundred

Question 89. What's The Date Object Using Javascript?

Answer :

Time internal a date object is stored as milliseconds for the reason that Jan 1, 1970.
New Date(06,01,02) // produces "Fri Feb 02 1906 00:00:00 GMT-0600 (Central Standard Time)"
new Date(06,01,02).ToLocaleString() // produces "Friday, February 02, 1906 00:00:00"
new Date(06,01,02) - new Date(06,01,01) // produces "86400000"

Question ninety. What Does The Delete Operator Do?

Answer :

The delete operator is used to delete all of the variables and gadgets used in the software ,however it does not delete variables declared with var key-word.

Question 91. How To Delete An Entry Using Javascript?

Answer :

The "delete" operator gets rid of an array detail, however oddly does now not exchange the scale of the array.
<script type="text/javascript">
var days = ["Sunday","Monday","Tuesday","Wednesday", "Thursday","Friday","Saturday"];
record.Write("Number of days:"+days.Duration); delete days[4];
document.Write("<br />Number of days:"+days.Duration);
</script>
This produces
Number of days:7
Number of days:7

Question ninety two. How To Use Strings As Array Indexes Using Javascript?

Answer :

Javascript does now not have a true hashtable object, however thru its wierdness, you could use the array as a hashtable.

file.Write("days["Monday"]:"+days["Monday"]);
</script>
This produces
days["Monday"]:Monday

Question 93. How To Use "be part of()" To Create A String From An Array Using Javascript?

Answer :

"be part of" concatenates the array factors with a targeted seperator between them.

Question ninety four. How To Make A Array As A Stack Using Javascript?

Answer :

The pop() and push() capabilities turn a innocent array into a stack

Question 95. How To Shift And Unshift Using Javascript?

Answer :

Question ninety six. What Does Break And Continue Statements Do?

Answer :

Continue declaration keeps the current loop (if label no longer unique) in a new new release while damage declaration exits the cutting-edge loop.

Question ninety seven. How To Create A Function Using Function Constructor?

Answer :

The following example illustrates this
It creates a function known as square with argument x and returns x improved by means of itself.
Var square = new Function ("x","return x*x");

Question 98. What's Prototypes For Javascript?

Answer :

Objects have "prototypes" from which they will inherit fields and features.

feature movie(title, director)
this.Identify = name "unknown"; //if null assign to "unknown"
this.ToString = movieToString; //assign feature to this approach pointer

movie.Prototype.IsComedy = false; //upload a area to the film's prototype
var officeSpace = new movie("OfficeSpace");
var narnia = new movie("Narni","Andrew Adamson");
report.Write(narnia.ToString());
report.Write("
Narnia a comedy? "+narnia.IsComedy);
officeSpace.IsComedy = true; //override the default only for this object
report.Write("
Office Space a comedy? "+officeSpace.IsComedy);
</script>

Question ninety nine. Unescape(), Escape()

Answer :

These are much like the decodeURI() and encodeURI(), however get away() is used for most effective portions of a URI.

If you use break out() for the entire URI... Nicely bad things take place.
<script type="text/javascript">
var uri = "http://www.Google.Com/search?Q=sonofusion Taleyarkhan"
record.Write("Original uri: "+uri);
report.Write("
escaped: "+get away(uri));
v/script>

Question a hundred. Decodeuri(), Encodeuri()

Answer :

Many characters can not be despatched in a URL, however need to be converted to their hex encoding. These capabilities are used to transform a whole URI (a superset of URL) to and from a layout that can be despatched through a URI.
<script type="text/javascript">
var uri = "http://www.Google.Com/search?Q=sonofusion Taleyarkhan"
report.Write("Original uri: "+uri);
record.Write("<br />encoded: "+encodeURI(uri));
</script>

Question a hundred and one. What Is The Difference Between Javascript And Jscript?

Answer :

Jscript helps extra wealthy set of capability/instructions than the java script, via which ActiveX and local computer can be accessed. These instructions are used in an intranet in which the connecting computer’s configuration is known and they may be all being accessed using Internet Explorer. While java script targets unknown machine configuration and Jscript can't for which java script are appropriate for internet which Jscripts aren't.

Question 102. What Is Java Script And What Are Their Functionalities?

Answer :

JavaScript is a consumer side scripting language this is specifically used to carry out purchaser facet processing to save you server round journeys and to make the consumer response time faster. It is widely used for validation motive along with confirm password validation and and so on. It is commonly embedded in the HTML which on consumer aspect is interpreted through the browser and the scripts are reproduction capable.

Question 103. What Is The Main Difference Between Client Side Javascript And Server Side Java Script? How Actually They Run On Both Side?

Answer :

To state the principle distinction, JavaScript on the customer side does now not require an internet server to make it run as a substitute it uses the customer’s processor for this motive. This eradicates the portability issue. But in server facet JavaScript deployment, portability, configuration are predominant and tremendous troubles and calls for an internet server to run the script within a page earlier than rendering its output as a reaction html page.

Question 104. What Are The Methods Of Validating Whether The Form Is Secure?

Answer :

Security of a shape can be ensured by several ways some of them are:-
1. Action Attribute of the shape- The form action attribute must begin with https:// for ensuring the at ease web site.
2. Checking the Java Routine- In the Java routine theformname.Movement="specific URL” which have to also begin with https:// for making sure the comfortable site.
Three. Checking the URL of the shape itself whether or not it begins with https://
Any one of the situation ought to be obeyed by means of the web shape else the shape isn't secured.

Question one hundred and five. How Can Javascript Make A Web Site Easier To Use?

Answer :