Problem to Convert a Javascript GTIN calculate function to VB.net

star_platinum

Hello, I am not able to convert this function to VB code.... This is the javascript function to get the last digit of a GTIN number:

factor = 3;
sum = 0;

var gNum = '1234564020233'

    for (index = gNum; index > 0; --index) {
        sum = sum + gNum.substring(index - 1, index) \* factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);

    result = gNum + cc;
   
    }

I have the problem to deal with the substring function. Anyone can help?

Dave Kreskowiak

OK, JavaScript substring returns the string enclosed by the start and ending values. In your case that would be index - 1, and index. It appears that index starts out with the length of the string in gNum and goes backwards by -1 with each iteration.

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Dave Kreskowiak

Dave Doknjas

factor = 3
sum = 0
Dim gNum As String = "1234564020233"

For index = gNum To 1 Step -1
sum = sum + gNum.Substring(index - 1, index - (index - 1)) * factor
factor = 4 - factor
Next index

cc = ((1000 - sum) Mod 10)
result = gNum + cc

David Anton Convert between VB, C#, C++, & Java www.tangiblesoftwaresolutions.com

star_platinum

Hi David, I got this error: System.Data.Index' is not accessible in this context because it is 'Private'.

Dave Doknjas

It must be due to 'index' not being declared. Try:

For index As Integer = gNum To 1 Step -1

David Anton Convert between VB, C#, C++, & Java www.tangiblesoftwaresolutions.com