Bank Account number verification using java

Question

I am trying to write a java program that verifies the validity of a bank account number in Algeria, and I was checking the web for formula, and I found a piece of javascript (that I could not understand).

Here is the code:

function validateFormRIB() {
  var x = document.forms["formrib"]["rib"].value;
  if ((!/^\d+$/.test(x))||(x.length!=20)) {
    alert("Le RIB doit comporter exactement 20 caractères numériques");
    return false;
  }
}

My question is what is the formula used for the computation?

Here is the link to the web page : http://www.babalweb.net/finance/verificateur-rib-releve-identite-bancaire-algerie.php

Answer 1

The "formula" you refer to is (I presume) this part

(!/^\d+$/.test(x))||(x.length!=20)

It has two parts:

(!/^\d+$/.test(x))

and

(x.length!=20)

The first part is a pattern match. It testing to see if the string in the variable x matches the regular expression /^\d+$/. That regex means

/    # start of regular expression
^    # match the start of the string
\d   # match one digit
+    # the previous pattern is matched one or more times
$    # match the end of the string
/    # end of regular expression.

In other words, "match a string that consists of one or more digits".

The second part is testing the string length.

Putting it all together, in context:

IF variable 'x' does not consist of one or more digits 
OR IF it does not have a length of 20
THEN show and 'alert' popup and return false.

---

The validation "formula" is easy to translate into Java ... or any other language with regex support.

However, it should be obvious that not every 20 digit number is actually a real Algerian bank account number.

(For what it is worth, the Wikipedia page on International Bank Account Numbers (IBANs) has a summary of formats for a number of countries. But it doesn't say anything more about Algerian bank numbers except that they are 20 digits.)