🔁 Classic ASP – Looping – Use For, While, and Do Loops in VBScript

🧲 Introduction – What Is Looping in Classic ASP?

Looping in Classic ASP lets you repeat blocks of code using VBScript until a condition is met. It’s essential for iterating through arrays, database records, or repeating HTML elements like lists and tables dynamically.

🎯 In this guide, you’ll learn:

• How to use For, For Each, While, and Do...Loop
• Syntax rules and examples
• When to use each type of loop
• Common mistakes and best practices

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🔁 For...Next Loop

Use when you know the number of iterations in advance.

<%
Dim i
For i = 1 To 5
    Response.Write "Item " & i & "<br>"
Next
%>

🧪 Output:

Item 1  
Item 2  
Item 3  
Item 4  
Item 5

---

🔁 For Each...Next Loop

Ideal for iterating over arrays or collections.

<%
Dim colors
colors = Array("Red", "Green", "Blue")

Dim color
For Each color In colors
    Response.Write color & "<br>"
Next
%>

🧪 Output:

Red  
Green  
Blue

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🔁 Do While...Loop

Executes the loop as long as the condition is true.

<%
Dim i
i = 1

Do While i <= 3
    Response.Write "Count: " & i & "<br>"
    i = i + 1
Loop
%>

🧪 Output:

Count: 1  
Count: 2  
Count: 3

---

🔁 Do...Loop While

Checks condition after running once. Guaranteed to execute at least once.

<%
Dim i
i = 1

Do
    Response.Write "Value: " & i & "<br>"
    i = i + 1
Loop While i <= 2
%>

🧪 Output:

Value: 1  
Value: 2

---

🧾 Example – Loop with Conditional Logic

<%
Dim scores
scores = Array(92, 75, 84)

Dim score
For Each score In scores
    If score >= 90 Then
        Response.Write "A (" & score & ")<br>"
    ElseIf score >= 80 Then
        Response.Write "B (" & score & ")<br>"
    Else
        Response.Write "C (" & score & ")<br>"
    End If
Next
%>

🧪 Output:

A (92)  
C (75)  
B (84)

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❌ Common Mistakes in ASP Looping

❌ Mistake	✅ Correction
Infinite loop (no exit condition)	Always update your counter inside loop
Missing Next, Loop, or Wend	Close all loops properly
Looping past array bounds	Use UBound() to limit array length

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🧩 Looping Over Form Values

<%
Dim field
For Each field In Request.Form
    Response.Write field & ": " & Request.Form(field) & "<br>"
Next
%>

🧪 Output:
Displays all POST form fields and their values.

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📘 Best Practices for Classic ASP Loops

✅ Do:

• Use For Each for cleaner array iteration
• Keep loop logic concise and well-indented
• Include exit logic to avoid infinite loops

❌ Avoid:

• Mixing loops with heavy business logic
• Forgetting to increment counters
• Modifying the looped collection during iteration

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📌 Summary – Recap & Next Steps

Looping is a core part of Classic ASP, allowing you to dynamically repeat output or logic. Mastering For, For Each, and Do While lets you build smarter, more efficient scripts.

🔍 Key Takeaways:

• Use For...Next when count is known
• Use For Each for arrays/collections
• Use Do While and Do Until for flexible looping

⚙️ Real-world Use Cases:

• Rendering lists or tables from arrays
• Looping through form fields or query strings
• Pagination, validation, and totals calculation

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❓ FAQs – Classic ASP Looping

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❓ Can I break out of a loop in VBScript?
✅ Yes, use Exit For or Exit Do to break the loop manually.

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❓ What’s the difference between While...Wend and Do While...Loop?
✅ Both work, but Do While is more flexible and preferred in Classic ASP.

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❓ How do I loop through a database recordset?
✅ Use Do Until rs.EOF with rs.MoveNext inside the loop.

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