Looping

 

Looping statements are used to execute the same block of code repeatedly for a fixed number of times or until a specific condition is met.

VBScript provides four types of looping statements:

For…Next loop – Executes code a specific number of times

For Each…Next loop – Executes code for each element in an array or collection

Do…Loop statement – Repeats code while or until a condition is met

While…Wend statement – Not recommended; use Do…Loop instead

 

The For…Next loop is used when you know in advance how many times the loop should run.

The For statement initializes the counter variable and defines the start and end values

The Next statement increments the counter by 1 each time the loop runs

Example:

 

<% For i = 0 To 5  Response.Write("The number is " & i & "
") Next %>

 

The Step keyword allows you to control how much the counter variable increases or decreases after each iteration.

Increasing the Counter

 

For i = 2 To 10 Step 2  some code Next

In this case, the value of i increases by 2 each time.

Decreasing the Counter

To decrease the value, use a negative Step and ensure the end value is smaller than the start value.

 

For i = 10 To 2 Step -2  some code Next

Here, the value of i decreases by 2 on each loop.

 

You can terminate a For…Next loop early using the Exit For statement.

 

For i = 1 To 10  If i = 5 Then Exit For  some code Next

The loop stops when i reaches 5.

 

The For Each…Next loop is used to iterate through all elements of an array or collection without using an index.

Example:

 

<% Dim cars(2) cars(0) = "Volvo" cars(1) = "Saab" cars(2) = "BMW" For Each x In cars  Response.Write(x & "
") Next %>

Each element in the cars array is printed one by one.

 

Use a Do…Loop when the number of iterations is not known in advance.

A Do…Loop can repeat code:

While a condition is true

Until a condition becomes true

 

Condition Checked Before Loop

 

Do While i > 10  some code Loop

If i is less than or equal to 10, the loop will not execute at all.

Condition Checked After Loop

 

Do  some code Loop While i > 10

This loop will execute at least once, even if the condition is false initially.

 

Condition Checked Before Loop

 

Do Until i = 10  some code Loop

If i is already 10, the loop will not run.

Condition Checked After Loop

 

Do  some code Loop Until i = 10

This loop executes at least one time, even if i equals 10.

 

You can stop a Do…Loop early using the Exit Do statement.

 

Do Until i = 10  i = i - 1  If i < 10 Then Exit Do Loop

The loop continues as long as i is not equal to 10 and remains greater than 10.