• Sub procedure
• Function procedure

VBScript Sub Procedures

A Sub procedure:

• is a series of statements, enclosed by the Sub and End Sub statements
• can perform actions, but does not return a value
• can take arguments
• without arguments, it must include an empty set of parentheses ()

or

VBScript Function Procedures

A Function procedure:

• is a series of statements, enclosed by the Function and End Function statements
• can perform actions and can return a value
• can take arguments that are passed to it by a calling procedure
• without arguments, must include an empty set of parentheses ()
• returns a value by assigning a value to its name

or

How to Call a Procedure

There are different ways to call a procedure. You can call it from within another procedure, on an event, or call it within a script.

Procedures can be used to get a variable value:

Here you call a Function called “findname”, the Function returns a value that will be stored in the variable “carname”.

Function procedures can calculate the sum of two arguments:

The function “myfunction” will return the sum of argument “a” and argument “b”. In this case 14.

When you call a procedure you can use the Call statement, like this:

Or, you can omit the Call statement, like this:

source from: w3schools

Conditional statements are used to perform different actions for different decisions.

In VBScript we have four conditional statements:

• If statement - executes a set of code when a condition is true
• If…Then…Else statement - select one of two sets of lines to execute
• If…Then…ElseIf statement - select one of many sets of lines to execute
• Select Case statement - select one of many sets of lines to execute

If…Then…Else

Use the If…Then…Else statement if you want to

• execute some code if a condition is true
• select one of two blocks of code to execute

If you want to execute only one statement when a condition is true, you can write the code on one line:

There is no ..Else.. in this syntax. You just tell the code to perform one action if a condition is true (in this case If i=10).

If you want to execute more than one statement when a condition is true, you must put each statement on separate lines, and end the statement with the keyword “End If”:

There is no ..Else.. in the example above either. You just tell the code to perform multiple actions if the condition is true.

If you want to execute a statement if a condition is true and execute another statement if the condition is not true, you must add the “Else” keyword:

In the example above, the first block of code will be executed if the condition is true, and the other block will be executed otherwise (if i is greater than 10).

If…Then…ElseIf

You can use the If…Then…ElseIf statement if you want to select one of many blocks of code to execute:

Select Case

You can also use the “Select Case” statement if you want to select one of many blocks of code to execute:

This is how it works: First we have a single expression (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each Case in the structure. If there is a match, the block of code associated with that Case is executed.

source from: w3schools

Looping statements are used to run the same block of code a specified number of times.

In VBScript we have four looping statements:

• For…Next statement - runs code a specified number of times
• For Each…Next statement - runs code for each item in a collection or each element of an array
• Do…Loop statement - loops while or until a condition is true
• While…Wend statement - Do not use it – use the Do…Loop statement instead

For…Next Loop

Use the For…Next statement to run a block of code a specified number of times.

The For statement specifies the counter variable (i), and its start and end values. The Nextstatement increases the counter variable (i) by one.

The Step Keyword

With the Step keyword, you can increase or decrease the counter variable by the value you specify.

In the example below, the counter variable (i) is INCREASED by two, each time the loop repeats.

To decrease the counter variable, you must use a negative Step value. You must specify an end value that is less than the start value.

In the example below, the counter variable (i) is DECREASED by two, each time the loop repeats.

Exit a For…Next

You can exit a For…Next statement with the Exit For keyword.

For Each…Next Loop

A For Each…Next loop repeats a block of code for each item in a collection, or for each element of an array.

Do…Loop

If you don’t know how many repetitions you want, use a Do…Loop statement.

The Do…Loop statement repeats a block of code while a condition is true, or until a condition becomes true.

Repeat Code While a Condition is True

You use the While keyword to check a condition in a Do…Loop statement.

If i equals 9, the code inside the loop above will never be executed.

The code inside this loop will be executed at least one time, even if i is less than 10.

Repeat Code Until a Condition Becomes True

You use the Until keyword to check a condition in a Do…Loop statement.

If i equals 10, the code inside the loop will never be executed.

The code inside this loop will be executed at least one time, even if i is equal to 10.

Exit a Do…Loop

You can exit a Do…Loop statement with the Exit Do keyword.

The code inside this loop will be executed as long as i is different from 10, and as long as i is greater than 10.

source from: w3schools

This tutorial has taught you how to add VBScript to your HTML pages, to make your web site more dynamic and interactive.

You have learned how to create variables and functions, and how to make different scripts run in response to different scenarios.

For more information on VBScript, please look at our VBScript examples and our VBScript references.

Now You Know VBScript, What’s Next?

The next step is to learn ASP.

While scripts in an HTML file are executed on the client (in the browser), scripts in an ASP file are executed on the server.

With ASP you can dynamically edit, change or add any content of a Web page, respond to data submitted from HTML forms, access any data or databases and return the results to a browser, customize a Web page to make it more useful for individual users.

Since ASP files are returned as plain HTML, they can be viewed in any browser.

If you want to learn more about ASP, please visit our ASP tutorial.

source from: w3schools

Before you continue you should have a basic understanding of the following:

• HTML / XHTML

If you want to study these subjects first, find the tutorials on our Home page.

What is VBScript?

• VBScript is a scripting language
• A scripting language is a lightweight programming language
• VBScript is a light version of Microsoft’s programming language Visual Basic
• VBScript is only supported by Microsoft’s browsers (Internet Explorer)

How Does it Work?

When a VBScript is inserted into an HTML document, Internet Explorer browser will read the HTML and interpret the VBScript. The VBScript can be executed immediately, or at a later event.

VBScript only works in Microsoft browsers (Internet Explorer).

source from: w3schools

Put a VBScript into an HTML Page

The example below shows how to use VBScript to write text on a web page:

The example below shows how to add HTML tags to the VBScript:

Example Explained

To insert a VBScript into an HTML page, we use the <script> tag. Inside the <script> tag we use the type attribute to define the scripting language.

So, the <script type=”text/vbscript”> and </script> tells where the VBScript starts and ends:

The document.write command is a standard VBScript command for writing output to a page.

By entering the document.write command between the <script> and </script> tags, the browser will recognize it as a VBScript command and execute the code line. In this case the browser will write Hello World! to the page:

How to Handle Simple Browsers

Browsers that do not support scripting, will display VBScript as page content.

To prevent them from doing this, the HTML comment tag should be used to “hide” the VBScript.

Just add an HTML comment tag <!– before the first VBScript statement, and a –> (end of comment) after the last VBScript statement, like this:

source from: w3schools

Where to Put the VBScript

VBScripts in a page will be executed immediately while the page loads into the browser. This is not always what we want. Sometimes we want to execute a script when a page loads, or at a later event, such as when a user clicks a button. When this is the case we put the script inside a function or a sub procedure, you will learn about procedures in a later chapter.

Scripts in <head>

Put your functions and sub procedures in the head section, this way they are all in one place, and they do not interfere with page content.

Scripts in <body>

If you don’t want your script to be placed inside a function, and especially if your script should write page content, it should be placed in the body section.

Scripts in <head> and <body>

You can place an unlimited number of scripts in your document, and you can have scripts in both the body and the head section.

Using an External VBScript

If you want to run the same VBScript on several pages, without having to write the same script on every page, you can write a VBScript in an external file.

Save the external VBScript file with a .vbs file extension.

Note: The external script cannot contain the <script> tag!

To use the external script, point to the .vbs file in the “src” attribute of the <script> tag:

Note: Remember to place the script exactly where you normally would write the script!

source from: w3schools

Do You Remember Algebra from School?

Do you remember algebra from school? x=5, y=6, z=x+y

Do you remember that a letter (like x) could be used to hold a value (like 5), and that you could use the information above to calculate the value of z to be 11?

These letters are called variables, and variables can be used to hold values (x=5) or expressions (z=x+y).

VBScript Variables

As with algebra, VBScript variables are used to hold values or expressions.

A variable can have a short name, like x, or a more descriptive name, like carname.

Rules for VBScript variable names:

• Must begin with a letter
• Cannot contain a period (.)
• Cannot exceed 255 characters

In VBScript, all variables are of type variant, that can store different types of data.

Declaring (Creating) VBScript Variables

Creating variables in VBScript is most often referred to as “declaring” variables.

You can declare VBScript variables with the Dim, Public or the Private statement. Like this:

Now you have created two variables. The name of the variables are “x” and “carname”.

You can also declare variables by using its name in a script. Like this:

Now you have also created a variable. The name of the variable is “carname”. However, this method is not a good practice, because you can misspell the variable name later in your script, and that can cause strange results when your script is running.

If you misspell for example the “carname” variable to “carnime”, the script will automatically create a new variable called “carnime”.  To prevent your script from doing this, you can use the Option Explicit statement. This statement forces you to declare all your variables with the dim, public or private statement.

Put the Option Explicit statement on the top of your script. Like this:

Assigning Values to Variables

You assign a value to a variable like this:

The variable name is on the left side of the expression and the value you want to assign to the variable is on the right. Now the variable “carname” has the value of “Volvo”, and the variable “x” has the value of “10″.

Lifetime of Variables

How long a variable exists is its lifetime.

When you declare a variable within a procedure, the variable can only be accessed within that procedure. When the procedure exits, the variable is destroyed. These variables are called local variables. You can have local variables with the same name in different procedures, because each is recognized only by the procedure in which it is declared.

If you declare a variable outside a procedure, all the procedures on your page can access it. The lifetime of these variables starts when they are declared, and ends when the page is closed.

VBScript Array Variables

An array variable is used to store multiple values in a single variable.

In the following example, an array containing 3 elements is declared:

The number shown in the parentheses is 2. We start at zero so this array contains 3 elements. This is a fixed-size array. You assign data to each of the elements of the array like this:

Similarly, the data can be retrieved from any element using the index of the particular array element you want. Like this:

You can have up to 60 dimensions in an array. Multiple dimensions are declared by separating the numbers in the parentheses with commas. Here we have a two-dimensional array consisting of 5 rows and 7 columns:

Asign data to a two-dimensional array:

source from: w3schools

The Session object

When you are working with an application on your computer, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you open the application and when you close it. However, on the internet there is one problem: the web server does not know who you are and what you do, because the HTTP address doesn’t maintain state.

ASP solves this problem by creating a unique cookie for each user. The cookie is sent to the user’s computer and it contains information that identifies the user. This interface is called the Session object.

The Session object stores information about, or change settings for a user session.

Variables stored in a Session object hold information about one single user, and are available to all pages in one application. Common information stored in session variables are name, id, and preferences. The server creates a new Session object for each new user, and destroys the Session object when the session expires.

When does a Session Start?

A session starts when:

• A new user requests an ASP file, and the Global.asa file includes a Session_OnStart procedure
• A value is stored in a Session variable
• A user requests an ASP file, and the Global.asa file uses the <object> tag to instantiate an object with session scope

When does a Session End?

A session ends if a user has not requested or refreshed a page in the application for a specified period. By default, this is 20 minutes.

If you want to set a timeout interval that is shorter or longer than the default, use the Timeoutproperty.

The example below sets a timeout interval of 5 minutes:

Use the Abandon method to end a session immediately:

Note: The main problem with sessions is WHEN they should end. We do not know if the user’s last request was the final one or not. So we do not know how long we should keep the session “alive”. Waiting too long for an idle session uses up resources on the server, but if the session is deleted too soon the user has to start all over again because the server has deleted all the information. Finding the right timeout interval can be difficult!

 Tip: Only store SMALL amounts of data in session variables!

Store and Retrieve Session Variables

The most important thing about the Session object is that you can store variables in it.

The example below will set the Session variable username to “Donald Duck” and the Session variable age to “50″:

When the value is stored in a session variable it can be reached from ANY page in the ASP application:

The line above returns: “Welcome Donald Duck”.

You can also store user preferences in the Session object, and then access that preference to choose what page to return to the user.

The example below specifies a text-only version of the page if the user has a low screen resolution:

Remove Session Variables

The Contents collection contains all session variables.

It is possible to remove a session variable with the Remove method.

The example below removes the session variable “sale” if the value of the session variable “age” is lower than 18:

To remove all variables in a session, use the RemoveAll method:

Loop Through the Contents Collection

The Contents collection contains all session variables. You can loop through the Contents collection, to see what’s stored in it:

Result:

If you do not know the number of items in the Contents collection, you can use the Count property:

Result:

Loop Through the StaticObjects Collection

You can loop through the StaticObjects collection, to see the values of all objects stored in the Session object:

source from: w3schools

The #include directive is used to create functions, headers, footers, or elements that will be reused on multiple pages.

How to Use the #include Directive

Here is a file called “mypage.asp”:

Here is the “wisdom.inc” file:

Here is the “time.inc” file:

If you look at the source code in a browser, it will look something like this:

Syntax for Including Files

To include a file in an ASP page, place the #include directive inside comment tags:

The Virtual Keyword

Use the virtual keyword to indicate a path beginning with a virtual directory.

If a file named “header.inc” resides in a virtual directory named /html, the following line would insert the contents of “header.inc”:

The File Keyword

Use the file keyword to indicate a relative path. A relative path begins with the directory that contains the including file.

If you have a file in the html directory, and the file “header.inc” resides in html\headers, the following line would insert “header.inc” in your file:

Note that the path to the included file (headers\header.inc) is relative to the including file. If the file containing this #include statement is not in the html directory, the statement will not work.

Tips and Notes

In the sections above we have used the file extension “.inc” for included files. Notice that if a user tries to browse an INC file directly, its content will be displayed. If your included file contains confidential information or information you do not want any users to see, it is better to use an ASP extension. The source code in an ASP file will not be visible after the interpretation. An included file can also include other files, and one ASP file can include the same file more than once.

Important: Included files are processed and inserted before the scripts are executed. The following script will NOT work because ASP executes the #include directive before it assigns a value to the variable:

You cannot open or close a script delimiter in an INC file. The following script will NOT work:

But this script will work:

source from: w3schools