kontonummer
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    2.0.0 • Public • Published

    Kontonummer

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    This is a reimagination of jop-io/kontonummer.js with some additional goals:

    • Provide an npm package with cjs and esm modules for easy use with node and bundlers.
    • Provide TypeScript definitions
    • Provide a similar API to Personnummer
    • Stretch goal: Calculate IBAN (and BIC/SWIFT-code)
    • Stretch goal: Handle BankGirot and PlusGirot numbers

    Some Code (c) Jonas Persson and Tobbe Lundberg which they have gracefully released under a MIT license. See LICENCE

    This implementation is written in TypeScript but the following specification should be applicable to other languages as well. But some language specific modifications may be required.

    Important Caveat

    As explained in the research section below there are some bank account numbers that is impossible to validate (as they do not have a check digit) that are indistinguishable from validatable accounts. I recommend using this library on form input fields but do not prevent form submission if the account number is reported as invalid. A good idea would be something like a warning saying "there is a chance this is not a valid bank account number you may want to double check."

    Specification [v1]

    Class

    The package should include a class that which should be the return value of parse

    class Kontonummer {
      constructor (sortingCode: string | number, accountNumber: string | number, options?: InitOptions)
      constructor (sortingCodeAndAccountNumber: string | number, options?: InitOptions)
    }
    • sortingCode (sv. clearing nummer) should be one of the following formats
      • SSSS
      • SSSS-C
    • accountNumber the allowed length varies, further explained in section Account Number White-space should be allowed in any position. Basically, only characters matches the regex /\d/ should be taken into consideration all other characters should be discarded.
    • sortingCodeAndAccountNumber should be one of the following formats (where S is sorting code, A is account number and C is a check digit. White-space should be allowed in any position. Basically, only characters matches the regex /\d/ should be taken into consideration all other characters should be discarded.
      • SSSS,AC
      • SSSSAC
      • S-C,AC
      • S-CAC
      • S-C,A-C
      • S-CA-C
      • etc.

    InitOptions

    • mode: 'strict' | 'semi' | 'lax'
      • strict should validate sorting code, account number length and account number check digit. Should throw if any of these checks fail.
      • semi should do strict checks for type 1 account numbers (4+7) but lax checks for type 2 account numbers.
      • lax should not throw if the check digit of the account number cannot be validated. Should instead set the valid property to false if the check digit or length is invalid. Should still throw for invalid sorting codes.

    Properties

    The class should expose the following properties once initialised

    class Kontonummer {
      readonly bankName: string
      readonly sortingCode: string
      readonly accountNumber: string
      readonly type: 1 | 2
      readonly comment: 1 | 2 | 3
      readonly valid: boolean // only relevant in `lax` mode
    }

    Errors

    All methods except for validate should throw an exception or return an error as a second return value. Error handling may be different depending on language. The exception/error class should be prefixed with Kontonummer.

    Parse

    The class should include a static parse method that creates a new instance of the class. It should take the same arguments as the class constructor. This function should also be an exported standalone method of the package.

    Pseudocode:

    class Kontonummer {
      static parse (...args) {
        return new Kontonummer(...args)
      }
    }
    
    export const parse = Kontonummer.parse

    Validate

    The class should include a static validate method that attempts to parse the provided input and returns a boolean that indicates if it succeeded. validate should not accept any options. This function should also be an exported standalone method of the package.

    Pseudocode:

    class Kontonummer {
      validate (sortingCode, accountNumber)
      validate (sortingCodeAndAccountNumber) {
        try {
          new Kontonummer(sortingCode, accountNumber)
          return true
        } catch {
          return false
        }
      }
    }
    
    export const validate = Kontonummer.validate

    Format

    Format key:

    • S: Sorting Code
    • A: Account number
    • C: Check digit
    • K: IBAN check digit
    • B: IBAN bank code

    The class should include a public format method that returns the sortingCode and accountNumber in one string. Some different formats should be available. If no argument is provided it should default to numeric.

    type Format = 'numeric' | 'pretty'
    type Part = 'full' | 'sortingCode' | 'accountNumber'
    
    class Kontonummer {
      format (format?: Format = 'numeric', part?: Part = 'full'): string
    }
    Name Format
    numeric
    (default)
    S[C]AC
    where the account number is padded to the appropriate max length depending on account type
    pretty Depends on type and bank, see research below

    [] brackets marks optional

    Research

    Moved to swantzter.se where I plan to publish research on other topics as well

    Install

    npm i kontonummer

    DownloadsWeekly Downloads

    78

    Version

    2.0.0

    License

    MIT

    Unpacked Size

    251 kB

    Total Files

    20

    Last publish

    Collaborators

    • swantzter