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    JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review
    JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review
    JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review
    Ebook215 pages2 hours

    JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review

    By equitypress

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    About this ebook

    The Ultimate JavaScript Reference & Learning Guide
    Over 100 Certification Questions, Answers, and Explanations

    One cannot claim fluency as a web developer without advanced knowledge of JavaScript, however, locating user-friendly yet comprehensive sources of reference can be challenging. With JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review, you can be in great shape to evaluate a potential job candidate, brush up on skills, or prepare for an interview. This guide will explain trouble shooting, applicability in websites and other applications, new features in 1.7, interactions with the host environment, and common errors. More than just Sun Microsystems documentation and sales pitches, this guide explains JavaScript from the perspective of the web developer so that you can evaluate a candidate or land a position with ease.

    Key topics include:

    *Changes from 1.6 to 1.7
    *Methods of interaction between JavaScript engines and host environments
    *Uses for stylizing or designing web based user interfaces
    *Security
    *Troubleshooting for many of the browsers in common use today, for instance PDAs and mobile phones

    LanguageEnglish
    Publisherequitypress
    Release dateJun 3, 2011
    ISBN9781603322348
    JavaScript Interview Questions, Answers, and Explanations: JavaScript Certification Review

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      JavaScript Interview Questions, Answers, and Explanations - equitypress

      Question 1: Image Loop

      I have a problem with the codes below:

      function curl(a){

      var i = 1

      if (a.substring(0,7)!='http://' || a.substring(a.length-3,a.length)!='gif')

      {

      alert(Error);

      }

      else

      {

      document.getElementById('dply').innerHTML='';

      for (i = 1; i < 6; i++){

      a=a.replace(*n*,i);

      document.getElementById('dply').innerHTML = document.getElementById('dply').innerHTML +

      '
      '+''+a+'> '+a+'>'+a+'';

      }

      }

      }

      text id=url size=40 value=http://www.eastman.ucl.ac.uk/guide/*n*.gif>

      button onclick=curl(document.getElementById('url').value)>

      dply>

      Why does the script above not go from 1.gif to 2.gif, 3.gif, 4.gif and 5.gif?

      A: When you call the function with the value http://www.eastman.ucl.ac.uk/guide/*n*.gif, the parameter a takes this value.

      In the first iteration, when i has the value 1, the statement a=a.replace(*n*,i); changes the value of a to http://www.eastman.ucl.ac.uk/guide/1.gif.

      In the next iterations, when i has the value 2, 3, 4 … the statement a=a.replace(*n*,i); will do nothing, because the string *n* is no longer part of a. The value of a (http://www.eastman.ucl.ac.uk/guide/1.gif) will remain unchanged.

      The script should be:

      function curl(a){

      var i = 1

      if (a.substring(0,7)!='http://' || a.substring(a.length-3,a.length)!='gif')

      {

      alert(Error);

      }

      else

      {

      document.getElementById('dply').innerHTML='';

      for (i = 1; i < 6; i++)

      {

      b=a;

      b=b.replace(*n*,i);

      document.getElementById('dply').innerHTML = document.getElementById('dply').innerHTML +

      '
      '+''+b+'> '+b+'>'+b+'';

      }

      }

      }

      text id=url size=40 value=http://www.eastman.ucl.ac.uk/guide/*n*.gif>

      button onclick=curl(document.getElementById('url').value)>

      dply>

      Inserting the statement b=a; allows the parameter a to always keep the initial value and the string *n* will be found and replaced with 2, 3, 4, and 5.

      Question 2: Autoredirect

      I am using PHP to explore the referring URL and then putting that as the location. The redirect code is as follows:

      $Refer[3] = newequip.php?ClientName=$ClientNameF;

      echo Add Equipment Results.$Refer[3].'\",2500)>;

      When I load it from the page already formatted with the ClientName in the URL, it redirects perfectly. I had it formatted by replacing the spaces with %20. The server side code from this page is as follows:

      location.href='\equipinfo.php?ClientName=Fox%20Theatre%20Hill&EquipName=T2',2500)>

      However, when I try to do the same from the other page, which needs to be sent back with the ClientName, it is not working. The client side code from this other page is as follows:

      location.href='\newequip.php?ClientName=Fox%20Theatre%20Hill',2500)>

      Why does it work for one page but not for the other?

      A: To make it work in both server and client side, edit the statement location .href='\newequip.php?ClientName=Fox%20Theatre%20Hill'

      The backslash n (\n) makes a new line in JavaScript. If you're using this on a web server, use a forward slash instead.

      Question 3: Selectbox onchange Disable Other Selectbox

      I have two select boxes, but I only want the user to be able to select one of them. Both boxes are dynamic and populate data from recordsets.

      Both boxes should be initially enabled. Once the user makes a selection in one of the boxes, the other should become disabled. If the user changes his mind and wants to select the other box, he should be able to select the first option (Option 0) in the box to re-enable the other box.

      The following is a sample code for select boxes to start with:

      frmFilter>

      How do I write a code that will allow the user to select only one box?

      A: This can probably be done in a more compact bit of code, but the following may be easier to understand and quicker than waiting for a difficult-to-read function.

      function chgSelect(which) {

      if (which == 'County') {

      if (document.getElementById('lstCounty').selectedIndex == 0) //Unlock lstCity

      document.getElementById('lstCity').disabled = false;

      else // lock city

      document.getElementById('lstCity').disabled = true;

      }

      else {

      if (document.getElementById('lstCity').selectedIndex == 0) //Unlock lstCounty

      document.getElementById('lstCounty').disabled = false;

      else // lock lstCounty

      document.getElementById('lstCounty').disabled = true;

      }

      }

      frmFilter>

      Question 4: Dynamic URL Links

      I have a JavaScript loop that gets a user’s settings, from which I would like to dynamically create the user’s html links on a web page. For example, the user selects certain companies. I will then create links to the companies he selected. How do I dynamically generate html links for a list of 5 to 10 items?

      A: Two of the many ways to dynamically generate html links are the following:

      CODE

      document.write('something.html>link');

      orCODE

      document.getElementById('linkContainer').innerHTML = 'something.html>link';

      linkContainer>

      Question 5: Can't Find Error in Simple JavaScript

      When I have the following JavaScript in my file and try to execute a function defined after it, the function is never executed. When I remove this piece, it works fine.

      function findOffset(alphabet, ch)

      {

      var findOffset = alphabet.indexOf(ch) - 1

      If (findOffset == -1) {

      return -5

      } else {

      return findOffset

      }

      }

      The part that gives me trouble is the If … Else statement. I have included the rest of the code to put it into context.

      Is there something wrong with the above code?

      A: Change the capital I in If to a lowercase i and rename the variable (it should not have the same name as the function).

      Your logic has a flaw in it, too. Because you subtract 1 from the index of a character, you could get a value of -2, if the character you're checking for is not in the string called alphabet.

      Putting some semicolon terminators in wouldn't go amiss either.

      Question 6: String Split

      I am using split() function on a string like this:

      var words = s.value.split( );

      but the above statement only splits on a blank space. I also want to split on : and -.

      The following statement didn’t work either:CODE

      var words = s.value.split( |:|-);

      How do I write the

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