Home > Articles > Open Source > Ajax & JavaScript

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Starting Your Script

By this time, you should be ready to start coding. You have decided what browsers you want to support, how you want to deal with non-supporting browsers, and where you want to store the scripts. This takes care of all of the technical aspects of writing JavaScript code. Now it is time to begin writing your scripts.

Defining Objectives

In your first script, we are going to create a simple pop-up dialog box that asks the user for a password. If the password is incorrect, the user is redirected to an error page. If the password is valid, the user is sent to the page he is requesting. Those whose browsers do not support JavaScript simply see a message saying they cannot access this page. Because this script is written in very basic JavaScript, it can be used in any supporting browser. For simplicity's sake, we also will keep all of our scripts inline rather than in an external source file.

Here is a quick summary of what we have decided:

  • Browser support: Support all.

  • Non-supporting browsers: Display a message saying they cannot access this portion of your site.

  • Location of script: Inline.

  • Objective: Prompt the user for a password when the page is accessed. If the correct password is entered, the user is redirected to the secure page. If an incorrect password is entered, the user is redirected to an error page.

Creating a Code Template

Now that our objectives are defined, the first thing we recommend you do is create a template. We usually include all the necessary <head> information and prepare the <body> portion in this template, which makes it extremely easy to add the necessary scripts and content. Listing 3.2 has a copy of the template I start with.

Listing 3.2 JavaScript Template File

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html 
   PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
 <meta http-equiv="Content-Script-Type" content="text/javascript" />
 <title>My First JavaScript Script</title>
 <script type="text/javascript" language="JavaScript">

 // Your code will go here...


<!-- Content starts here -->


Handling Non-Supporting Browsers

The first thing we want to get out of the way in this example is how we will handle non-supporting browsers. Because we are not performing an excessive amount of XHTML for these users, it will be quick and easy to finish. The following snippet shows what will be included in this section.

   Sorry, but your browser either does not support JavaScript or you
    have it turned off. For information on JavaScript supporting browsers
   or how to turn it back on, please see the website of your browser's

As you can see, this was a very simple task, creating a message that will be displayed to the user. We included the text within bold tags (<b>...</b>) to ensure that it will show up well on the page.

Writing Your Code

At this point the page is ready. Now we just need to write the necessary JavaScript code. By accomplishing all of the other tasks first, such as defining our objectives, creating a template, and handling non-supporting browsers, we have made sure that the page functions properly without any scripting on it. This is an important step; on many occasions we thought that our script had a problem when in fact we had not properly closed an XHTML element, or we had misplaced some comments.

For this example, we will be working in the <head> portion of the page. The first thing we need to do is create a dialog box for the user to enter the password. For this task, we will use the prompt() method. This will give us a dialog like the one shown in Figure 3.4 to pass the entered information back to our script.

Figure 3.4 The prompt() dialog box.

The prompt() method is a method of the window object, and it takes two parameters that combine to have the following syntax:


When using this method, you should replace message with instructions for the user. This will be displayed above the field where the user will enter his data. The default parameter is used to specify a default set of text for the user. In our first script, we do not want to have a default, so we will simply pass it an empty string.

The key to using this dialog box is that it returns what the user enters. Using the information entered, we can check to see, in our example, if the proper password was typed. Based on this data we can redirect the user's browser appropriately.

In addition to the prompt() method, we will also be using the location property of the window object. We will set this property to redirect the browser to the appropriate page according to the success of the user's entry. The last thing we need to note is that we will include all of this code in a function that is called after the entire page has loaded.

The code that accomplishes this task is relatively short and can be seen in the following block:

<script type="text/javascript" language="JavaScript">
 function passCheck(){
  if(prompt("Please enter your password","") == "letmein"){
   window.location = "/secure.html";
   window.location = "/error.html";

Looking at this code, you see that we have defined a function called passCheck(). Within this function, we use an if..else conditional statement to verify the password entered by the user. Don't worry too much right now about how this works—it is covered in detail in Chapter 6, "Control Structures and Looping." All you need to understand at this point is that it is checking to see if the user entered "letmein" as the password. The == evaluation operator, which will be covered in Chapter 5, "Operators," performs this task.

If the user enters the correct password, he is redirected to the /secure.html page. If the user does not enter the correct password, his browser is redirected to the /error.html page.

Calling the Function

The last step in getting our script to work is to call the function. For this, we will use the onLoad event handler within the <body> element to call the function after the page is loaded. This event handler will be invoked, as mentioned, after the page finishes loading, at which time it will call the passCheck() function we defined. This entire line should look like the following:

<body onload="passCheck()">
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020