VBScript ReadyState Property

last modified April 9, 2025

The ReadyState property in VBScript is used with the XMLHTTP object to track the state of HTTP requests. It indicates the current status of the request/response process. This property is essential for asynchronous operations where you need to monitor progress.

ReadyState returns integer values from 0 to 4 representing different stages. It enables proper handling of asynchronous requests by signaling state changes. This tutorial covers ReadyState with practical examples to demonstrate its usage.

ReadyState Property Overview

The ReadyState property has five possible values representing different states. Each value corresponds to a specific stage in the HTTP request lifecycle. The property is read-only and changes as the request progresses.

The states are: 0 (UNINITIALIZED), 1 (LOADING), 2 (LOADED), 3 (INTERACTIVE), and 4 (COMPLETED). Monitoring these states allows for proper request handling. Understanding these states is crucial for effective asynchronous programming.

Basic ReadyState Monitoring

This example demonstrates basic monitoring of the ReadyState property. It shows how to check the state during an HTTP request. The script makes a simple GET request and outputs state changes.

basic_readystate.vbs

Set xmlhttp = CreateObject("MSXML2.XMLHTTP")
xmlhttp.Open "GET", "https://example.com", True
xmlhttp.OnReadyStateChange = GetRef("HandleStateChange")
xmlhttp.Send

Sub HandleStateChange()
    WScript.Echo "ReadyState: " & xmlhttp.readyState
    If xmlhttp.readyState = 4 Then
        WScript.Echo "Request completed with status: " & xmlhttp.status
    End If
End Sub

While xmlhttp.readyState <> 4
    WScript.Sleep 100
Wend

The script creates an XMLHTTP object and initiates an asynchronous GET request. The OnReadyStateChange event handler outputs state changes. When the state reaches 4 (COMPLETED), it displays the HTTP status code.

Synchronous Request with ReadyState

This example shows using ReadyState with a synchronous request. Although synchronous requests block execution, checking ReadyState can still be useful. The script demonstrates state progression in a simple sync request.

sync_readystate.vbs

Set xmlhttp = CreateObject("MSXML2.XMLHTTP")
xmlhttp.Open "GET", "https://example.com", False
xmlhttp.Send

WScript.Echo "Initial ReadyState: " & xmlhttp.readyState
WScript.Echo "After Send ReadyState: " & xmlhttp.readyState

If xmlhttp.readyState = 4 Then
    WScript.Echo "Response: " & Left(xmlhttp.responseText, 100)
End If

The script makes a synchronous GET request to example.com. It outputs the ReadyState before and after sending the request. With synchronous requests, the state immediately jumps to 4 after Send().

Handling Different ReadyStates

This example demonstrates handling all possible ReadyState values. It provides specific actions for each state change. The script shows how to implement comprehensive state monitoring.

all_states.vbs

Set xmlhttp = CreateObject("MSXML2.XMLHTTP")
xmlhttp.Open "GET", "https://example.com", True
xmlhttp.OnReadyStateChange = GetRef("StateHandler")
xmlhttp.Send

Sub StateHandler()
    Select Case xmlhttp.readyState
        Case 0: WScript.Echo "UNINITIALIZED: Object created"
        Case 1: WScript.Echo "LOADING: Open() called"
        Case 2: WScript.Echo "LOADED: Send() called, headers received"
        Case 3: WScript.Echo "INTERACTIVE: Downloading response"
        Case 4: 
            WScript.Echo "COMPLETED: Request finished"
            If xmlhttp.status = 200 Then
                WScript.Echo "Success: " & Left(xmlhttp.responseText, 50)
            End If
    End Select
End Sub

While xmlhttp.readyState <> 4
    WScript.Sleep 100
Wend

The script implements a detailed state handler for all ReadyState values. Each case provides specific feedback about the request progress. When the request completes (state 4), it checks the status code and displays part of the response.

Error Handling with ReadyState

This example demonstrates error handling in conjunction with ReadyState monitoring. It shows how to detect and handle request failures. Proper error handling ensures robust HTTP operations.

error_handling.vbs

Set xmlhttp = CreateObject("MSXML2.XMLHTTP")
xmlhttp.Open "GET", "https://nonexistent.example", True
xmlhttp.OnReadyStateChange = GetRef("ErrorHandler")
xmlhttp.Send

Sub ErrorHandler()
    If xmlhttp.readyState = 4 Then
        If xmlhttp.status = 200 Then
            WScript.Echo "Request successful"
        Else
            WScript.Echo "Error " & xmlhttp.status & ": " & xmlhttp.statusText
        End If
    End If
End Sub

While xmlhttp.readyState <> 4
    WScript.Sleep 100
Wend

The script attempts to request a non-existent URL. When the request completes (state 4), it checks the status code. If not 200, it displays the error code and description. This pattern is essential for reliable HTTP operations.

ReadyState with POST Request

This example shows using ReadyState with a POST request. It demonstrates state monitoring while sending data to a server. The script includes setting request headers and handling the response.

post_request.vbs

Set xmlhttp = CreateObject("MSXML2.XMLHTTP")
xmlhttp.Open "POST", "https://example.com/api", True
xmlhttp.setRequestHeader "Content-Type", "application/json"
xmlhttp.OnReadyStateChange = GetRef("PostHandler")
xmlhttp.Send "{""key"":""value""}"

Sub PostHandler()
    If xmlhttp.readyState = 4 Then
        WScript.Echo "Response status: " & xmlhttp.status
        WScript.Echo "Response body: " & xmlhttp.responseText
    End If
End Sub

While xmlhttp.readyState <> 4
    WScript.Sleep 100
Wend

The script sends a JSON payload via POST to an API endpoint. It sets the appropriate Content-Type header. The handler waits for completion (state 4) then displays the status and response. This pattern works for various API interactions.

Source

XMLHTTP Documentation

In this article, we have explored the ReadyState property in VBScript, covering its usage and practical applications. From basic monitoring to error handling and POST requests, these examples demonstrate robust HTTP request management. With this knowledge, you can implement reliable asynchronous operations in your VBScript projects.

Author

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

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