Vb script tutorial
- 1. VBScript Tutorial VBScript is a Microsoft scriptinglanguage. What is VBScript? VBScriptisa scriptinglanguage A scriptinglanguage isalightweightprogramminglanguage VBScriptisa lightversionof Microsoft'sprogramminglanguage Visual Basic How Does it Work? When a VBScript is inserted into a HTML document, the Internet browser will read the HTML and interpret the VBScript. The VBScript can be executed immediately, or at a later event. Write text <html> <body> <script type="text/vbscript"> document.write("HellofromVBScript!") </script> </body> </html> VBScript Where To place Head section Scripts can be placed in the head section. Usually we put all the "functions" in the head section. The reason for this is to be sure that the script is loaded before the function is called. <html> <head> <script type="text/vbscript"> alert("Hello") </script> </head> <body> <p> We usuallyuse the head sectionfor "functions". The reason for thisis to be sure that the script is loadedbefore the function is called. </p> </body> </html>
- 2. Body section Execute a script that is placed in the body section. Scripts in the body section are executed when the page is loading. <html> <body> <script type="text/vbscript"> document.write("Scriptsinthe body sectionare executedwhenthe page is loading") </script> </body> </html> VBScript Variables A variable is a "container" for information you want to store. A variable's value can change during the script. You can refer to a variable by name to see its value or to change its value. In VBScript, all variables are of type variant, that can store different types of data. Rules for Variable Names: Must beginwitha letter Cannotcontaina period(.) Cannotexceed255 characters Declaring Variables You can declare variables with the Dim, Public or the Private statement. Like this: dim name name=some value Array Variables dim names(2) 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: names(0)="Tove" names(1)="Jani"
- 3. names(2)="Stale" 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: VBScript Procedures We have two kinds of procedures: The Sub procedure and the Function procedure. A Sub procedure: isa seriesof statements,enclosedbythe SubandEnd Substatements can performactions,but doesnot return a value can take argumentsthat are passedtoit bya callingprocedure withoutarguments,mustincludeanemptyset of parentheses() Sub mysub() some statements End Sub or Sub mysub(argument1,argument2) some statements End Sub 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 Function myfunction() some statements myfunction=some value End Function or Function myfunction(argument1,argument2) some statements myfunction=some value End Function dim table(4, 6)
- 4. <html> <head> <script type="text/vbscript"> sub mySub() msgbox("Thisisa sub procedure") endsub </script> </head> <body> <script type="text/vbscript"> call mySub() </script> <p>A sub procedure doesnot return a result.</p> </body> </html> <html> <head> <script type="text/vbscript"> functionmyFunction() myFunction = "BLUE" endfunction </script> </head> <body> <script type="text/vbscript"> document.write("Myfavorite coloris" & myFunction()) </script> <p>A functionprocedure CAN return a result.</p> </body> </html> VBScript Conditional Statements Conditional Statements Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this. In VBScript we have three conditional statements: if statement- use thisstatementif youwantto execute asetof code whena conditionistrue if...then...else statement- use thisstatementif youwantto selectone of twosetsof linesto execute
- 5. if...then...elseif statement- use thisstatementif youwanttoselectone of manysetsof linesto execute selectcase statement- use thisstatementif youwantto selectone of manysetsof linesto execute If....Then.....Else You should use the If...Then...Else statement if you want to execute some code if aconditionistrue selectone of twoblocks 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: if i=10 Then msgbox "Hello" There is no ..else.. in this syntax. You just tell the code to perform one action if the 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": if i=10 Then msgbox "Hello" i = i+1 end If There is no ..else.. in this syntax 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: if i=10 then msgbox "Hello" else msgbox "Goodbye" end If The first block of code will be executed if the condition is true, and the other block will be executed otherwise (if i is not equal to 10).
- 6. If....Then.....Elseif You can use the if...then...elseif statement if you want to select one of many blocks of code to execute: if payment="Cash" then msgbox "You are going to pay cash!" elseif payment="Visa" then msgbox "You are going to pay with visa." elseif payment="AmEx" then msgbox "You are going to pay with American Express." else msgbox "Unknown method of payment." end If Select Case You can also use the SELECT statement if you want to select one of many blocks of code to execute: select case payment case "Cash" msgbox "You are going to pay cash" case "Visa" msgbox "You are going to pay with visa" case "AmEx" msgbox "You are going to pay with American Express" case Else msgbox "Unknown method of payment" end select 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. VBScript Looping Statements Looping Statements Very often when you write code, you want to allow the same block of code to run a number of times. You can use looping statements in your code to do this. In VBScript we have four looping statements: For...Nextstatement- runsstatementsaspecifiednumberof times.
- 7. For Each...Next statement- runsstatementsforeachitemina collectionoreachelementof an array Do...Loop statement- loopswhile oruntil aconditionistrue While...Wendstatement- Donot use it - use the Do...Loopstatementinstead For...Next Loop You can use a For...Next statement to run a block of code, when you know how many repetitions you want. You can use a counter variable that increases or decreases with each repetition of the loop, like this: For i=1 to 10 some code Next The For statement specifies the counter variable (i) and its start and end values. The Next statement increases the counter variable (i) by one. Step Keyword Using 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. For i=2 To 10 Step 2 some code Next 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. For i=10 To 2 Step -2 some code Next Exita For...Next You can exit a For...Next statement with the Exit For keyword.
- 8. 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. dim cars(2) cars(0)="Volvo" cars(1)="Saab" cars(2)="BMW" For Each x in cars document.write(x & "<br />") Next Do...Loop You can use Do...Loop statements to run a block of code when you do not know how many repetitions you want. The block of code is repeated while a condition is true or until a condition becomes true. RepeatingCodeWhileaConditionisTrue You use the While keyword to check a condition in a Do...Loop statement. Do While i>10 some code Loop If i equals 9, the code inside the loop above will never be executed. Do some code Loop While i>10 The code inside this loop will be executed at least one time, even if i is less than 10. RepeatingCodeUntil a ConditionBecomesTrue You use the Until keyword to check a condition in a Do...Loop statement. Do Until i=10 some code Loop If i equals 10, the code inside the loop will never be executed.
- 9. Do some code Loop Until i=10 The code inside this loop will be executed at least one time, even if i is equal to 10. Exita Do...Loop You can exit a Do...Loop statement with the Exit Do keyword. Do Until i=10 i=i-1 If i<10 Then Exit Do Loop 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.