Top 50 Html+javascript Interview Questions You Must Prepare 20.Jul.2024

Q1. How To Access An External Javascript File That Is Stored Externally And Not Embedded?

This can be achieved by using the following tag between head tags or between body tags.

<script src="abc.js"></script>

 where abc.js is the external javscript file to be accessed.

 

Q2. How Do You Target A Specific Frame From A Hyperlink?

Include the name of the frame in the target attribute of the hyperlink. <a href=”mypage.htm” target=”myframe”>>My Page</a>

Q3. How Do I Make A Frame With A Vertical Scrollbar But Without A Horizontal Scrollbar?

The only way to have a frame with a vertical scrollbar but without a horizontal scrollbar is to define the frame with SCROLLING="auto" (the default), and to have content that does not require horizontal scrolling. There is no way to specify that a frame should have one scrollbar but not the other. Using SCROLLING="yes" will force scrollbars in both directions (even when they aren't needed), and using SCROLLING="no" will inhibit all scrollbars (even when scrolling is necessary to access the frame's content). There are no other values for the SCROLLING attribute.

Q4. What Are The Problems Associated With Using Javascript, And Are There Javascript Techniques That You Discourage?

Browser version incompatibility is the biggest problem. It requires knowing how each scriptable browser version implements its object model. You see, the incompatibility rarely has to do with the core JavaScript language (although there have been improvements to the language over time); the bulk of incompatibility issues have to do with the object models that each browser version implements. For example, scripters who started out with Navigator 3 implemented the image rollover because it looked cool. But they were dismayed to find out that the image object wasn't scriptable in Internet Explorer 3 or Navigator @While there are easy workarounds to make this feature work on newer browsers without disturbing older ones, it was a painful learning experience for many. 

The second biggest can of worms is scripting connections between multiple windows. A lot of scripters like to have little windows pop up with navigation bars or some such gizmos. But the object models, especially in the older browser versions, don't make it easy to work with these windows the minute you put a user in front of them--users who can manually close windows or change their stacking order. More recently, a glitch in some uninstall routines for Windows 95 applications can disturb vital parts of the system Registry that Internet Explorer 4 requires for managing multiple windows. A scripter can't work around this problem, because it's not possible to detect the problem in a user's machine. I tend to avoid multiple windows that interact with each other.

Q5. How Is Javascript Different From Java?

JavaScript was developed by Brendan Eich of Netscape; Java was developed at Sun Microsystems. While the two languages share some common syntax, they were developed independently of each other and for different audiences. Java is a full-fledged programming language tailored for network computing; it includes hundreds of its own objects, including objects for creating user interfaces that appear in Java applets (in Web browsers) or standalone Java applications. In contrast, JavaScript relies on whatever environment it's operating in for the user interface, such as a Web document's form elements. 

JavaScript was initially called LiveScript at Netscape while it was under development. A licensing deal between Netscape and Sun at the last minute let Netscape plug the "Java" name into the name of its scripting language. Programmers use entirely different tools for Java and JavaScript. It is also not uncommon for a programmer of one language to be ignorant of the other. The two languages don't rely on each other and are intended for different purposes. In some ways, the "Java" name on JavaScript has confused the world's understanding of the differences between the two. On the other hand, JavaScript is much easier to learn than Java and can offer a gentle introduction for newcomers who want to graduate to Java and the kinds of applications you can develop with it.

Q6. How Do I Keep People From Stealing My Source Code And/or Images?

Because copies of your HTML files and images are stored in cache, it is impossible to prevent someone from being able to save them onto their hard drive. If you are concerned about your images, you may wish to embed a watermark with your information into the image. Consult your image editing program's help file for more details.

The colors on my page look different when viewed on a Mac and a PC. The Mac and the PC use slightly different color palettes. There is a 216 "browser safe" color palette that both platforms support; the Microsoft color picker page has some good information and links to other resources about this. In addition, the two platforms use different gamma (brightness) values, so a graphic that looks fine on the Mac may look too dark on the PC. The only way to address this problem is to tweak the brightness of your image so that it looks acceptable on both platforms.

Q7. Methods Get And Post In Html Forms - What's The Difference?

  • GET: Parameters are passed in the querystring. Maximum amount of data that can be sent via the GET method is limited to about 2kb.
  • POST: Parameters are passed in the request body. There is no limit to the amount of data that can be trferred using POST. However, there are limits on the maximum amount of data that can be trferred in one name/value pair.

Q8. How To Create A Function Using Function Constructor?

The following example illustrates this
It creates a function called square with argument x and returns x multiplied by itself.
var square = new Function ("x","return x*x");

Q9. When I Try To Upload My Site, All My Images Are X's. How Do I Get Them To Load Correctly?

They are a few reasons that this could happen. The most common are:

  1. You're attempting to use a .bmp or .tif or other non-supported file format. You can only use .gif and .jpg on the web. You must convert files that are not .gif or .jpg into a .gif or .jpg with your image/graphics program.
  2. You've forgotten to upload the graphic files. Double-Check.
  3. You've incorrectly linked to the images. When you are starting out, try just using the file name in the tag. If you have cat.jpg, use 
  4. img src="cat.jpg">.
  5. Image file names are case-sensitive. If your file is called CaT.JpG, you cannot type cat.jpg, you must type CaT.JpG exactly in the src.
  6. If all of the above fail, re-upload the image in BINARY mode. You may have accidentally uploaded the image in ASCII mode.

Q10. Is There A Site That Shows Which Tags Work On Which Browsers?

There have been several attempts to do this, but I'm not aware of any really good source of comparisons between the browsers. The trouble is that there are many different versions of each browser, and many different tags. All current browsers should support the tags in the official HTML 3.2 specification, but the major ones also support nonstandard tags and sometimes have slightly different implementations. One place that has fairly good compatibility info is Browsercaps. 

Q11. What Does The Enableviewstatemac Setting In An Aspx Page Do?

Setting EnableViewStateMac=true is a security measure that allows ASP.NET to ensure 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 in the value of viewstate that was sent to the browser, it raises an error - Validation of viewstate MAC failed. 

Use <%@ Page EnableViewStateMac="true"%> to set it to true (the default value, if this attribute is not specified is also true) in an aspx page.

Q12. What Can Javascript Programs Do?

Generation of HTML pages on-the-fly without accessing the Web server. The user can be given control over the browser like User input validation Simple computations can be performed on the client's machine The user's browser, OS, screen size, etc. can be detected Date and Time Handling

Q13. How To Determine The State Of A Checkbox Using Javascript?

var checkedP = window.document.getElementById("myCheckBox").checked;

Q14. How To Set The Focus In An Element Using Javascript?

<script> function setFocus() { if(focusElement != null) { document.forms[0].elements["myelementname"].focus(); } } </script>

 

Q15. How Do You Convert Numbers Between Different Bases In Javascript?

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

Q16. How Can I Display An Image On My Page?

Use an IMG element. The SRC attribute specifies the location of the image. The ALT attribute provides alternate text for those not loading images. For example:
<img src="logo.gif" alt="ACME Products">

Q17. How To Write A Script For "select" Lists Using Javascript

@To remove an item from a list set it to null.
mySelectObject.options[3] = null; 

@To truncate a list set its length to the maximum size you desire.
mySelectObject.length = 2; 

@To delete all options in a select object set the length to 0. 
mySelectObject.leng

Q18. What Are Javascript Types?

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

Q19. How To Set A Html Document's Background Color?

document.bgcolor property can be set to any appropriate color.

Q20. What Is Negative Infinity?

It’s a number in JavaScript, derived by dividing negative number by zero.

Q21. What Does "1"+2+4 Evaluate To?

Since 1 is a string, everything is a string, so the result is 124. 

Q22. How Do I Make Sure My Framed Documents Are Displayed Inside Their Frame Set?

When the sub-documents of a frameset state are accessed directly, they appear without the context of the surrounding frameset.
If the reader's browser has JavaScript support enabled, the following script will restore the frameset:
<SCRIPT TYPE="text/javascript">
if (parent.location.href == self.location.href) {
if (window.location.href.replace)
window.location.replace('frameset.html');
else
// causes problems with back button, but works
window.location.href = 'frameset.html';
}
</SCRIPT> 
A more universal approach is a "restore frames" link:
<A HREF="frameset.html" TARGET="_top">Restore Frames 
Note that in either case, you must have a separate frameset document for every content document. If you link to the default frameset document, then your reader will get the default content document, rather than the content document he/she was trying to access. These frameset documents should be generated automatically, to avoid the tedium and inaccuracy of creating them by hand. 
Note that you can work around the problem with bookmarking frameset states by linking to these separate frameset documents using TARGET="_top", rather than linking to the individual content documents.

 

Q23. How Do I Create Frames? What Is A Frameset?

Frames allow an author to divide a browser window into multiple (rectangular) regions. Multiple documents can be displayed in a single window, each within its own frame. Graphical browsers allow these frames to be scrolled independently of each other, and links can update the document displayed in one frame without affecting the others. 

You can't just "add frames" to an existing document. Rather, you must create a frameset document that defines a particular combination of frames, and then display your content documents inside those frames. The frameset document should also include alternative non-framed content in a NOFRAMES element. 

The HTML 4 frames model has significant design flaws that cause usability problems for web users. Frames should be used only with great care.

Q24. What Is The Data Type Of Variables Of In Javascript?

All variables are of object type in JavaScript. 

Q25. What Does Break And Continue Statements Do?

Continue statement continues the current loop (if label not specified) in a new iteration whereas break statement exits the current loop.

 

Q26. What Is The Difference Between A Web-garden And A Web-farm?

Web-garden - An IIS6.0 feature where you can configure an application pool as a web-garden and also specify the number of worker processes for that pool. It can help improve performance in some cases. 

Web-farm - a general term referring to a cluster of physically separate machines, each running a web-server for scalability and performance (contrast this with web-garden which refers to multiple processes on one single physical machine).

Q27. How Do I Get Out Of A Frameset?

If you are the author, this is easy. You only have to add the TARGET attribute to the link that takes readers to the intended 'outside' document. Give it the value of _top. 

In many current browsers, it is not possible to display a frame in the full browser window, at least not very easily. The reader would need to copy the URL of the desired frame and then request that URL manually. 

I would recommend that authors who want to offer readers this option add a link to the document itself in the document, with the TARGET attribute set to _top so the document displays in the full window if the link is followed.

Q28. How Can Javascript Be Used To Personalize Or Tailor A Web Site To Fit Individual Users?

JavaScript allows a Web page to perform "if-then" kinds of decisions based on browser version, operating system, user input, and, in more recent browsers, details about the screen size in which the browser is running. While a server CGI program can make some of those same kinds of decisions, not everyone has access to or the expertise to create CGI programs. For example, an experienced CGI programmer can examine information about the browser whenever a request for a page is made; thus a server so equipped might serve up one page for Navigator users and a different page for Internet Explorer users. Beyond browser and operating system version, a CGI program can't know more about the environment. But a JavaScript-enhanced page can instruct the browser to render only certain content based on the browser, operating system, and even the screen size. 

Scripting can even go further if the page author desires. For example, the author may include a preference screen that lets the user determine the desired background and text color combination. A script can save this information on the client in a well-regulated local file called a cookie. The next time the user comes to the site, scripts in its pages look to the cookie info and render the page in the color combination selected previously. The server is none the wiser, nor does it have to store any visitor-specific information.

Q29. Are There Any Problems With Using Frames?

The fundamental problem with the design of frames is that framesets create states in the browser that are not addressable. Once any of the frames within a frameset changes from its default content, there is no longer a way to address the current state of the frameset. It is difficult to bookmark - and impossible to link or index - such a frameset state. It is impossible to reference such a frameset state in other media. When the sub-documents of such a frameset state are accessed directly, they appear without the context of the surrounding frameset. Basic browser functions (e.g., printing, moving forwards/backwards in the browser's history) behave differently with framesets. Also, browsers cannot identify which frame should have focus, which affects scrolling, searching, and the use of keyboard shortcuts in general. 

Furthermore, frames focus on layout rather than on information structure, and many authors of framed sites neglect to provide useful alternative content in the NOFRAMES element. Both of these factors cause accessibility problems for browsers that differ significantly from the author's expectations and for search engines.

Q30. How To Make A Array As A Stack Using Javascript?

The pop() and push() functions turn a harmless array into a stack
<script type="text/javascript">
var numbers = ["one", "two", "three", "four"];
numbers.push("five");
numbers.push("six");
document.write(numbers.pop());
document.write(numbers.pop());
document.write(numbers.pop());
</script>
This produces
sixfivefour

Q31. Why Do My Links Open New Windows Rather Than Update An Existing Frame?

If there is no existing frame with the name you used for the TARGET attribute, then a new browser window will be opened, and this window will be assigned the name you used. Furthermore, TARGET="_blank" will open a new, unnamed browser window. 

In HTML 4, the TARGET attribute value is case-insensitive, so that abc and ABC both refer to the same frame/window, and _top and _TOP both have the same meaning. However, most browsers treat the TARGET attribute value as case-sensitive and do not recognize ABC as being the same as abc, or _TOP as having the special meaning of _top. 

Also, some browsers include a security feature that prevents documents from being hijacked by third-party framesets. In these browsers, if a document's link targets a frame defined by a frameset document that is located on a different server than the document itself, then the link opens in a new window instead.

Q32. What Is A Tag?

In HTML, a tag tells the browser what to do. When you write an HTML page, you enter tags for many reasons -- to change the appearance of text, to show a graphic, or to make a link to another page.

 

Q33. How Do I Update Two Frames At Once?

There are two basic techniques for updating multiple frames with a single link: The HTML-based technique links to a new frameset document that specifies the new combination of frames. The JavaScript-based solution uses the onClick attribute of the link to update the additional frame (or frames).
The HTML-based technique can link to a new frameset document with the TARGET="_top" attribute (replacing the entire frameset). However, there is an alternative if the frames to be updated are part of a nested frameset. In the initial frameset document, use a secondary frameset document to define the nested frameset. For example:
<frameset cols="*,3*">
<frame src="contents.html" name="Contents">
<frame src="frameset2.html" name="Display">
<noframes>
<!-- Alternative non-framed version -->
</body></noframes>
</frameset>
A link can now use the TARGET="Display" attribute to replace simultaneously all the frames defined by the frameset2.html document. 
The JavaScript-based solution uses the onClick attribute of the link to perform the secondary update. For example: 
<a href="URL1" target="Frame1" onClick="top.Frame2.location='URL2';">Update frames 
The link will update Frame1 with URL1 normally. If the reader's browser supports JavaScript (and has it enabled), then Frame2 will also be updated (with URL2).

 

Q34. Are Java And Javascript The Same?

No.java and javascript are two different languages.
Java is a powerful object - oriented programming language like C++,C whereas Javascript is a client-side scripting language with some limitations.

Q35. What Is The Difference Between Sessionstate And Viewstate?

ViewState is specific to a page in a session. Session state refers to user specific data that can be accessed across all pages in the web application.

 

Q36. What Does The "access Is Denied" Ie Error Mean?

The "Access Denied" error in any browser is due to the following reason.
A javascript in one window or frame is tries to access another window or frame whose document's domain is different from the document containing the script.

Q37. In A Pop-up Browser Window, How Do You Refer To The Main Browser Window That Opened It?

Use window.opener to refer to the main window from pop-ups.

Q38. What Is The Difference Between An Alert Box And A Confirmation Box?

An alert box displays only one button which is the OK button whereas the Confirm box displays two buttons namely OK and cancel.

Q39. Are You Concerned That Older Browsers Don't Support Javascript And Thus Exclude A Set Of Web Users? Individual Users?

Fragmentation of the installed base of browsers will only get worse. By definition, it can never improve unless absolutely everyone on the planet threw away their old browsers and upgraded to the latest gee-whiz versions. But even then, there are plenty of discrepancies between the scriptability of the latest Netscape Navigator and Microsoft Internet Explorer. 

The situation makes scripting a challenge, especially for newcomers who may not be aware of the limitations of earlier browsers. A lot of effort in my books and ancillary material goes toward helping scripters know what features work in which browsers and how to either workaround limitations in earlier browsers or raise the compatibility common denominator. 

Designing scripts for a Web site requires making some hard decisions about if, when, and how to implement the advantages scripting offers a page to your audience. For public Web sites, I recommend using scripting in an additive way: let sufficient content stand on its own, but let scriptable browser users receive an enhanced experience, preferably with the same HTML document.

Q40. Can Javascript Code Be Broken In Different Lines?

Breaking is possible within a string statement by using a backslash at the end but not within any other javascript statement.that is ,
document.write("Hello world");

is possible but not document.write
("hello world");

Q41. What And Where Are The Best Javascript Resources On The Web?

 The best place to start is something called the meta- which provides a high-level overview of the JavaScript help available on the Net. 

For interactive help with specific problems, nothing beats the primary JavaScript Usenet newsgroup, comp.lang.javascript. Netscape and Microsoft also have vendor-specific developer discussion groups as well as detailed documentation for the scripting and object model implementations.

Q42. How To Create Arrays In Javascript?

We can declare 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 access them by using their index number. Note that index number starts from @To get the third element of the array we have to use the index number 2 . Here is the way to get the third element of an array. 
document.write(scripts[2]); 
We also can create an array like this 
var no_array = new Array(21, 22, 23, 24, 25);

Q43. What Is A Prompt Box?

A prompt box allows the user to enter input by providing a text box.

Q44. Text From Your Clipboard?

It is true, text you last copied for pasting (copy & paste) can be stolen when you visit web sites using a combination of JavaScript and ASP (or PHP, or CGI) to write your possible sensitive data to a database on another server.

 

Q45. How To Shift And Unshift Using Javascript?

<script type="text/javascript">
var numbers = ["one", "two", "three", "four"];
numbers.unshift("zero");
document.write(" "+numbers.shift());
document.write(" "+numbers.shift());
document.write(" "+numbers.shift());
</script>
This produces
zero one two
shift, unshift, push, and pop may be used on the same array. Queues are easily implemented using combinations.

Q46. What Does Isnan Function Do?

Return true if the argument is not a number.

Q47. What Web Sites Do You Feel Use Javascript Most Effectively (i.e., Best-in-class Examples)? The Worst?

The best sites are the ones that use JavaScript so trparently, that I'm not aware that there is any scripting on the page. The worst sites are those that try to impress me with how much scripting is on the page.

Q48. What Is Javascript?

JavaScript is a general-purpose programming language designed to let programmers of all skill levels control the behavior of software objects. The language is used most widely today in Web browsers whose software objects tend to represent a variety of HTML elements in a document and the document itself. But the language can be--and is--used with other kinds of objects in other environments. For example, Adobe Acrobat Forms uses JavaScript as its underlying scripting language to glue together objects that are unique to the forms generated by Adobe Acrobat. Therefore, it is important to distinguish JavaScript, the language, from the objects it can communicate with in any particular environment. When used for Web documents, the scripts go directly inside the HTML documents and are downloaded to the browser with the rest of the HTML tags and content. 

JavaScript is a platform-independent,event-driven, interpreted client-side scripting and programming language developed by Netscape Communications Corp. and Sun Microsystems.

Q49. How To Embed Javascript In A Web Page?

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

Q50. What Is A Hypertext Link?

A hypertext link is a special tag that links one page to another page or resource. If you click the link, the browser jumps to the link's destination.