VBScript sample: Connect Four

Connect Four Sample

Automatic component download

Connect Four demonstrates automatic component download, which is part of the ActiveX platform. The page requires to ActiveX Controls to be installed. When the page loads, the browser checks to see if the controls are installed already. If they're not, then the browser uses a system-provided component download service to download and install the controls automatically.

To make this work, the HTML for Connect Four includes information that tells the browser where to get the controls. This is specified using the CODEBASE attribute, which is part of the OBJECT tag. In this case, two servers are required: ThreeD32.ocx and InTimer.ocx.

Here are the OBJECT tags that use the CODEBASE attribute:

<OBJECT ID=Square16 
		CLASSID="clsid:0BA686B9-F7D3-101A-993E-0000C0EF6F5E" 
		HEIGHT=30 WIDTH=30 
		CODEBASE="/vbscript/us/vbssamp/commoncode/threed32.ocx">
	</OBJECT>

	<lOBJECT ID=TimerControl
		CODEBASE="/vbscript/us/vbssamp/commoncode/intimer.ocx"
		CLASSID="clsid:59CCB4A0-727D-11CF-AC36-00AA00A47DD2" 
		HEIGHT=30 WIDTH=120> 
		<PARAM NAME="TimeOut" Value = 1000>
	</OBJECT>

Using Visual Basic 4.0 to target VBScript

Visual Basic 4.0 is a useful tool for building solutions that use VBScript. Since VBScript is a strict subset of VB, VB can easily be used to build complex web-based solutions. Connect Four was developed and debugged using VB4. This section provides some simple tips for using VB4 to debug VBScript-based solutions.

Tip: Stick to the subset. VBScript is missing some of the features of Visual Basic, so you need to stick to the subset when developing VBScript-based solutions. VBScript is a pretty complete subset so this isn't very hard. Types, ByRef parameters, and records are a few of the more important omissions.

Tip: Put all the code in one VB form. Its easiest to move code between VBScript and VB if all of the code is in one form. During development, it is common to copy all the code from the form and paste it wholesale into the HTML, in-between "<SCRIPT>" and "<SCRIPT>".

Tip: Use the HTML intrinsic controls on VB forms. Internet Explorer 3.0 uses ActiveX Controls for the HTML intrinsics. You can use these in Visual basic 4.0 too. To do so, just reference HTMLCtl.ocx, which you'll find in your windows/system directory once you've installed IE3.