kontonummer
v4.0.1
Published
A validator for swedish banking numbers
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Kontonummer
This is a reimagination of jop-io/kontonummer.js with some additional goals:
- 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 formatsSSSS
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 (whereS
is sorting code,A
is account number andC
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 thevalid
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 CodeA
: Account numberC
: Check digitK
: IBAN check digitB
: 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