VBScript

 VBScript  What is VBScript?  An interpreted programming language primarily used to write relatively short programs that access operating system and application objects. The VBScript commands are a subset of the more complete, compiled Visual Basic language. Different from compiled code.  Why VBScript?  VBScript is an easy to learn language and thus is a good candidate for a brief introduction to programming.  VBScript can be used to automate tasks in web pages, MS Excel spreadsheets, MS Access Databases, and other MS applications.   VBScript can be used to automate administrative tasks such as moving or copying files, creating user accounts, tweak the registry etc.  Advantages of using VBScript It can be embedded with other types of code. Shorter edit-debugging cycle. Ideally suited for quick-ad hoc solutions. Good platform coverage. Disadvantages of using VBScript It’s going to be slower than programming language No protection from snooping and change Syntax errors aren’t caught until runtime Harder to debug since no development environment is available by default  Variables and Variable Declaration  A variable is a place in the computer memory where your script holds a piece (or pieces) of  information, or data. Behind the scenes, the variable is a reserved section of the computer’s memory for storing data.  VBScript does not require variable declaration by default.  Variables in VBScript can be declared anywhere in a program as long as it is before that  variable is referenced. Unlike most languages, variables declared in VBScript are “variant” and do not assume a type (string, long, double, integer, Boolean) until the first time they are assigned a value.  Variables in VBScript can be declared using: 1. 2. 3. 4.

dim or dimension public private const or constant

Data Types  VBScript is loosely Typed  Variant- An all-purpose, universal, super data type. But a full range of Variant “subtypes” is available.  A Variant variable automatically chooses its subtype whenever you place a new value into it. It does this by examining the value placed into it and making its best guess about what the appropriate subtype is.

 A Variant variable has exactly one subtype; in other words, the Variant’s subtype can only be one type at a time.  Variant Subtypes

Testing for and Coercing Subtypes:   VarType() and TypeName() built-in VBScript functions allow to check the subtype of an  Variant variable. Implicit Type Coercion is when a Variant variable changes its subtype automatically   Avoiding Trouble with Implicit Type Coercion Built-in VBScript Functions

 Arrays as Complex Data Types  Array is a matrix of data  Array can have up to 60 dimensions The lower bound of an array is always zero  Array Bounds 1. LBound 2. UBound  Working with arrays How to declare and populate an array  Dim Names(9) ‘ Declare an array with 10 elements. Dim Names() ‘ Declare a dynamic array. Dim A   A = Array(10,20,30) B = A(2) ’ B is now 30 How to add dimensions and elements to an array dynamically  The ReDim statement is used to size or resize a dynamic array that has already been formally  declar declared ed using using a Priva Private, te, Publi Public, c, or Dim statem statement ent with with em empty pty parent parenthes heses es (with (without out dimension subscripts). subscripts). You can use the ReDim statement repeatedly to change the number of  elements and dimensions in an array. If you use the Preserve keyword, you can resize only the last array dimension, and you can’t change the number of dimensions at all. For example, if your array has only one dimension,  you can resize that dimension because it is the last and only dimension. However, if your array has two or more dimensions, you can change the size of only the last dimension and still preserve the contents of the array. The following example shows how you can increase the size of the last dimension of a dynamic array without erasing any existing data contained in the array.

ReDim X(10, 10, 10) ReDim Preserve X(10, 10, 15) How to loop through an array and access all of its contents Dim A   A = Array(10,20,30) For i = 0 To UBound(A) MsgBox A(i) Next Dim A   A = Array(10,20,30) For Each element in A  MsgBox element Next Erasing arrays Dim NumArray(9) Dim DynamicArray() ReDim DynamicArray(9) ‘ Allocate Allocate storage storage space. Erase NumArray NumArray ‘ Each element is reinitialized. reinitialized. Erase DynamicArray DynamicArray ‘ Free memory used used by by array. Using VarType with arrays. Dim A   A = Array(10,20,30) MsgBox VarType(A) The VarType function never returns the value for Array by itself. It is always added to some other value to indicate an array of a particular type. The value for Variant is only returned  when it has been added to the value for Array to indicate that the argument to the VarType function is an array. For example, the value returned for an array of integers is calculated as 12 + 8192, or 8204. Operators and Operator Precedence Precedence

Operator Precedence The operations are normally performed from left to right 1. ∩, −, (*, /), \, Mod, (+, −) 2. & 3. =, , , =, Is

4. Not, And, Or, Xor, Eqv, Imp Importance of parentheses parentheses Math Operations

String Concatenation Concatenation Strings in VBScript can be concatenated (connected) using either the + or & operators  A = “Hello” B = “World” MsgBox A & ” ” & B & “!”  A = “Hello” B = “World” MsgBox A + ” ” + B + “!”  A = InputBox(“Enter your first name”) B = InputBox(“Enter your last name”) MsgBox A & ” ” & B Control of Flow  Branching logic If.. End If  Select.. End Select If Then < other code goes here > ElseIf Then < some other code goes here > Else < some other code goes here > End If  Use Nested If’s, but with caution! c aution! Select Case < expression > Case

< code goes here > Case < other code goes here > Case < other code goes here > Case Else < other code goes here > End Select Be cautious of Nested Select Case too!! Make the best decision between If.. End If and Select Case.. End Select Looping logic For.. Next For Each.. Next Do.. While  While.. Wend For…Next Ideal for two situations:  When you want to execute a block of code repeatedly a known, finite number of times.  When you want to execute a block of code once for each element in a complex data structure such as an array, file, or database table. Examples with the keyword ‘Step’ For i = 10 To 0 Step -2 MsgBox i Next Step – Amount counter is changed each time through the loop. If not specified, step defaults to one. For Each…Next The For Each…Next loop is a special kind of loop that is specifically used for traversing collections Do Loop The Do loop is the most versatile of all the loop constructs. You can easily make it loop as many times as you like based on any criteria you like.

Executing the Block at Least Once Testing a Precondition Choosing Between Until and While Breaking out of a Do Loop  While.. Wend  While  Wend Points to remember in While…Wend statement: 1. No option of using either WHILE of UNTIL 2. No equivalent to EXIT FOR or EXIT DO

Procedures and Functions: Procedures and functions allow you to modularize the code in your script into named blocks that perform specific functions. Modularization allows you to think about a more complex problem in a structured way, increases the readability and understandability of your code. Creates opportunities to reuse the same code multiple times in the same script. Procedure Syntax [Public|Private] Sub Name ([Argument1],[ArgumentN]) ([Argument1],[ArgumentN]) [ code inside the procedure ] End Sub Function Syntax [Public|Private] Function Name ([Argument1],[ArgumentN]) [ code inside the function ] End Function Usage of ByRef and ByVal In a Sub or Function declaration, each parameter can be specified as ByRef or ByVal. If  neither is specified, the default is ByRef. If ByVal ByVal is speci specifie fied, d, the corres correspon pondin ding g argum argument ent is always always passed passed by value value when when the subroutine is called.

If ByRef (or neither) is specified, the argument can be passed by reference or by value when the subroutine is called. The argument is passed by value if it is enclosed in parentheses, and if the parentheses do not apply to the parameter list. The argument is also passed by value if  the variable sent as an argument is in a class. Otherwise, it is passed by reference. Sub IncrementByRef(ByRef Value)  Value = Value + 1 End Sub Sub IncrementByVal(ByVal Value)  Value = Value + 1 End Sub

Dim Num Num = 10 MsgBox “Num : ” & Num IncrementByRef(Num)) : MsgBox “IncrementByRef(Num) IncrementByRef(Num “IncrementByRef(Num) : ” & Num IncrementByRef Num : MsgBox “IncrementByRef Num : ” & Num IncrementByVal(Num)) : MsgBox “IncrementByVal(Num) : ” & Num IncrementByVal(Num IncrementByVal Num : MsgBox “IncrementByVal Num : ” & Num Error Handling Error handling is the programmer’s programmer’s main line of o f defense against unpredictability. The term error handling refers not only to how a program program responds responds when an error occurs,  but also to how it prevents errors from happening in the first place. Types of Errors Syntax Errors: Halt the execution of the script. Runtime Errors: Occur when a command attempts to perform an action that is invalid Logic Errors: Produce undesirable results- contaminating data, confusing users, causing other logic and runtime errors to occur or obscuring the real source of a problem Syntax Errors Syntax errors tend to pop up in several circumstances:

 When something is missing from the code — parentheses, keywords (especially those that define blocks), parameters — or when some element of this code is simply out of place  When a keyword, statement, or procedure call is misspelled or used incorrectly   When you try to use a Visual Basic or VBA keyword or function that is not implemented by   VBScript  When you use keywords that are not supported by a particular version of the script engine. Runtime Errors The error does not offend offend the VBScript VBScript runtime runtime engine during compilation; compilation; rather, the runtime engine has a problem with the execution of the code Divided into 3 categories: Native VBScript runtime errors Examples for divide by zero and assigning Null value

Non-VBScript runtime errors Errors from other sources- namely, scripting scripting hosts such as IIS and  Variable declaration runtime errors related to the Option Explicit directive Errors Related to Option Explicit; with the usage of Option Explicit directive, one needs to declare all the variable before using them Logic Errors The best way to deal with them is to avoid them in the first place Develop Defensive Programming Handling Errors Taking an active, rather than passive, approach when responding to errors, including having extra code built into your script to deal with errors in case they occur. Elements necessary for handling errors Err Intrinsic object with global scope Methods: Clear() Raise() Properties:

On Error Statements Switch that controls the error control settings Flipping the Error Handling Switch On Error Resume Next On Error GoTo 0 Setting Traps for Errors On Error Resume Next Err.Number On Error GoTo 0 Generating Custom Errors Err.Raise  When Not to Use Err.Raise Distinguish between an error and a problem message Report and error when there is some problem in your script or in something outside of your script. E.g. Divide by zero error  When to Generate Custom Errors  When a rule is broken; an assumption fails. Generate an error. Class In object object-or -orien iented ted program programmin ming, g, a class class is a constr construct uct that is used used as a bluepr blueprint int (or template) to create objects of that class. This blueprint describes the state and behavior that the objects of the class all share. An object of a given class is called an instance of the class. The class that contains (and was used to create) that instance can be considered as the type of  that object, e.g. an object instance of the “Fruit” class would be of the type “Fruit”. Class Customer Private m_CustomerName m_CustomerName Private m_OrderCount

Private Sub Class_Initialize m_CustomerName m_CustomerName = “” m_OrderCount = 0 End Sub ‘ CustomerName property. Public Property Get CustomerName CustomerName CustomerName CustomerName = m_CustomerName m_CustomerName End Property  Public Property Let CustomerName(custname) m_CustomerName m_CustomerName = custname End Property  ‘ OrderCount property (read only). Public Property Get OrderCount OrderCount = m_OrderCount m_OrderCount End Property  ‘ Methods. Public Sub IncreaseOrders(valuetoincrease) IncreaseOrders(valuetoincrease) m_OrderCount = m_OrderCount + valuetoincrease End Sub End Class Dim c Set c = New Customer c.CustomerName c.CustomerName = “Fabrikam, Inc.” MsgBox (c.CustomerName) (c.CustomerName) c.IncreaseOrders(5) c.IncreaseOrders(3) MsgBox (c.OrderCount) The Scripting Runtime Objects Creating Objects Elements of Objects The “With” Keyword Objects can have multiple references Object Lifetime and D Destroying estroying Objects The Dictionary Object  A Dictionary object is the equivalent of a PERL associative array. Items can be any form of  data, and are stored in the array. Each item is associated with a unique key. The key is used to retrieve an individual item and is usually an integer or a string, but can be anything except an array.  Array Vs Dictionary  Example to create a Dictionary object Dim d ‘ Create a variable. Set d = CreateObject(“Scripting.Dictionary”) CreateObject(“Scripting.Dictionary”) d.Add “a”, “Athens” ‘ Add some keys and items.

d.Add “b”, “Belgrade” d.Add “c”, “Cairo” a = d.Items ‘ Get the keys. For i = 0 To d.Count -1 ‘ Iterate the array. msgbox a(i) Next a = d.Items ‘ Get the items. For i = 0 To d.Count -1 ‘ Iterate the array. msgbox a(i) Next Three Different Ways to Add Be careful with the ITEM property 

The FileSystemObject Library 

Examples Creating a Folder2 different ways Set FSO=CreateObject(“Scripting.File FSO=CreateObject(“Scripting.Filesystemobject”) systemobject”) Set objFolder=FSO.GetFolder(“C:\”) objFolder=FSO.GetFolder(“C:\”) objFolder.SubFolders.Add objFolder.SubFolders.Add “Test1″ Copying a File FSO.CopyFile “\\A_Network_Folder\*.xls”, “\\A_Network_Folder\*.xls”, _ “C:\MyFolder\Spreadsheets\”, “C:\MyFolder\Spreadsheets\”, True Copying a Folder Reading a Text File ReadAll() Read() ReadLine()  Writing to a Text File forWriting forAppending Regular Expressions Expressions Provide powerful facilities for character pattern-matching and replacing. Building on Simplicity  String manipulation functions vs Regular Expressions. The RegExp Object Properties: Global Property  IgnoreCase Property  Pattern Property  Methods:

Execute Property  Replace Property  Test Property 

Matching a whole class of characters Replacing Digits Replacing everything but Digits  Anchoring and Shorting a Pattern 3 special characters that anchor a patter: ^ used outside of [] $ \b Using Repeat Counts Example with and without repeat counts Note: re.Global=True is not an alternative for repeat counts Specifying a Minimum Number or Range of Matches “\d+” “\d*” “\d?” Remembered Matches

Is simply part of a pattern Useful when you want to use some or all of the text that matched your pattern as part of the replacement text. Execute Method Replace Method Can also replace subexpressions subexpressions in the pattern. Backreferencing Example Test Method The Matches Collection -Contains regular expression Match objects -Each Match object provides access to three things: The string found by the regular expression The length of the string  An index to where the match was found Note: Remember to set the Global property to True Matches Properties Properties 1. Count 2. Item Miscellaneous String Functions Instr() InstrRev() Join() Left() Right() Mid() Split() Ltrim() Rtrim () StrComp() Len() Date Functions: Now() Date()

Day() Month()  Year() Hour() Minute() Second() Time()