From ce8a94c3e82a221e938b96594c1e8858f0b7c012 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 27 Aug 2025 15:27:01 +0200
Subject: [PATCH 01/11] Add utility function isValidSwissIbanNumber

---
 CHANGELOG.md           |  4 ++++
 src/lib/string.spec.ts | 14 +++++++++++++-
 src/lib/string.ts      | 30 ++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c15e1c6..e0dfef1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `isValidSwissIbanNumber` string utility function
+
 ## [2.0.0] - 2025-07-29
 
 ### Added
diff --git a/src/lib/string.spec.ts b/src/lib/string.spec.ts
index 94fc71e..8bab2ea 100644
--- a/src/lib/string.spec.ts
+++ b/src/lib/string.spec.ts
@@ -1,4 +1,4 @@
-import { isNullOrEmpty, isNullOrWhitespace, capitalize, uncapitalize, truncate } from "./string";
+import { isNullOrEmpty, isNullOrWhitespace, capitalize, uncapitalize, truncate, isValidSwissIbanNumber } from "./string";
 
 describe("string tests", () => {
   test.each([
@@ -120,4 +120,16 @@ describe("string tests", () => {
   ])("truncate without suffix parameter", (value, maxLength, expected) => {
     expect(truncate(value, maxLength)).toBe(expected);
   });
+
+  test.each([
+    [null as unknown as string, false],
+    [undefined as unknown as string, false],
+    ["CH9300762011623852957", true],
+    ["CH93 0000 0000 0000 0000 1", false],
+    ["ch93 0076 2011 6238 5295 7", false],
+    ["DE93 0076 2011 6238 5295 7", false],
+    ["CH93 0076 2011 6238 5295 7", true],
+  ])("Is IBAN valid", (unformattedIbanNumber, expected) => {
+    expect(isValidSwissIbanNumber(unformattedIbanNumber)).toBe(expected);
+  });
 });
diff --git a/src/lib/string.ts b/src/lib/string.ts
index c0666b3..28d9d74 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -64,3 +64,33 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
 
   return `${value.slice(0, maxLength)}${suffix}`;
 }
+
+/**
+ * Checks if the provided string is a valid swiss IBAN number
+ * @param iBanNumber The provided IBAN number to check
+ * @returns The result of the IBAN number check
+ */
+export function isValidSwissIbanNumber(iBanNumber: string): boolean {
+  if (!isNullOrEmpty(iBanNumber)) {
+    const compactIban = iBanNumber.replaceAll(/\s+/g, "");
+    if (!/^CH\d{19}$/.test(compactIban)) return false;
+    const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4).toString();
+
+    const numericStr = Array.from(rearrangedIban, (ch) => {
+      if (/[A-Z]/.test(ch)) {
+        const code = ch.codePointAt(0);
+        // code is never undefined!
+        return (code! - 55).toString();
+      }
+      return ch;
+    }).join("");
+
+    let restOfCalculation = 0;
+    for (const digit of numericStr) {
+      restOfCalculation = (restOfCalculation * 10 + Number(digit)) % 97;
+    }
+
+    return restOfCalculation === 1;
+  }
+  return false;
+}

From 1114fda81b67438c35730b9fc5b4727666323aa0 Mon Sep 17 00:00:00 2001
From: "Sandro C." <sc@neolution.ch>
Date: Wed, 27 Aug 2025 16:05:16 +0200
Subject: [PATCH 02/11] Update src/lib/string.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/lib/string.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index 28d9d74..5538350 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -66,7 +66,7 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
 }
 
 /**
- * Checks if the provided string is a valid swiss IBAN number
+ * Checks if the provided string is a valid Swiss IBAN number
  * @param iBanNumber The provided IBAN number to check
  * @returns The result of the IBAN number check
  */

From bba833b0f68bbdf8eaebfab39910e991b06ce4c5 Mon Sep 17 00:00:00 2001
From: "Sandro C." <sc@neolution.ch>
Date: Wed, 27 Aug 2025 16:05:41 +0200
Subject: [PATCH 03/11] Update src/lib/string.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/lib/string.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index 5538350..9c1aa8f 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -74,7 +74,7 @@ export function isValidSwissIbanNumber(iBanNumber: string): boolean {
   if (!isNullOrEmpty(iBanNumber)) {
     const compactIban = iBanNumber.replaceAll(/\s+/g, "");
     if (!/^CH\d{19}$/.test(compactIban)) return false;
-    const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4).toString();
+    const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4);
 
     const numericStr = Array.from(rearrangedIban, (ch) => {
       if (/[A-Z]/.test(ch)) {

From 2e788ea9d4b64da00c15e22c038acc43d44e3439 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 27 Aug 2025 16:11:34 +0200
Subject: [PATCH 04/11] Changed test name

---
 src/lib/string.spec.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/string.spec.ts b/src/lib/string.spec.ts
index 8bab2ea..e4e4d67 100644
--- a/src/lib/string.spec.ts
+++ b/src/lib/string.spec.ts
@@ -129,7 +129,7 @@ describe("string tests", () => {
     ["ch93 0076 2011 6238 5295 7", false],
     ["DE93 0076 2011 6238 5295 7", false],
     ["CH93 0076 2011 6238 5295 7", true],
-  ])("Is IBAN valid", (unformattedIbanNumber, expected) => {
+  ])("Is Swiss IBAN valid", (unformattedIbanNumber, expected) => {
     expect(isValidSwissIbanNumber(unformattedIbanNumber)).toBe(expected);
   });
 });

From 7afe6cf6e97cf1c913bd5cdbae3f3af5410874a1 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 27 Aug 2025 16:27:13 +0200
Subject: [PATCH 05/11] Fix

---
 src/lib/string.ts | 39 ++++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index 9c1aa8f..00eb0c4 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -71,26 +71,27 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
  * @returns The result of the IBAN number check
  */
 export function isValidSwissIbanNumber(iBanNumber: string): boolean {
-  if (!isNullOrEmpty(iBanNumber)) {
-    const compactIban = iBanNumber.replaceAll(/\s+/g, "");
-    if (!/^CH\d{19}$/.test(compactIban)) return false;
-    const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4);
-
-    const numericStr = Array.from(rearrangedIban, (ch) => {
-      if (/[A-Z]/.test(ch)) {
-        const code = ch.codePointAt(0);
-        // code is never undefined!
-        return (code! - 55).toString();
-      }
-      return ch;
-    }).join("");
-
-    let restOfCalculation = 0;
-    for (const digit of numericStr) {
-      restOfCalculation = (restOfCalculation * 10 + Number(digit)) % 97;
+  if (isNullOrEmpty(iBanNumber)) {
+    return false;
+  }
+  const compactIban = iBanNumber.replaceAll(/\s+/g, "");
+  if (!/^CH\d{19}$/.test(compactIban)) {
+    return false;
+  }
+  const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4);
+  const numericStr = Array.from(rearrangedIban, (ch) => {
+    if (/[A-Z]/.test(ch)) {
+      const code = ch.codePointAt(0);
+      // code is never undefined!
+      return (code! - 55).toString();
     }
+    return ch;
+  }).join("");
 
-    return restOfCalculation === 1;
+  let restOfCalculation = 0;
+  for (const digit of numericStr) {
+    restOfCalculation = (restOfCalculation * 10 + Number(digit)) % 97;
   }
-  return false;
+
+  return restOfCalculation === 1;
 }

From 86335efb1324176f5446e906d781e3e44ce1b86f Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Thu, 28 Aug 2025 07:48:53 +0200
Subject: [PATCH 06/11] Changed parameter name and added is null or whitespace
 check

---
 src/lib/string.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index 00eb0c4..3aa0315 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -67,14 +67,14 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
 
 /**
  * Checks if the provided string is a valid Swiss IBAN number
- * @param iBanNumber The provided IBAN number to check
+ * @param ibanNumber The provided IBAN number to check
  * @returns The result of the IBAN number check
  */
-export function isValidSwissIbanNumber(iBanNumber: string): boolean {
-  if (isNullOrEmpty(iBanNumber)) {
+export function isValidSwissIbanNumber(ibanNumber: string): boolean {
+  if (isNullOrWhitespace(ibanNumber)) {
     return false;
   }
-  const compactIban = iBanNumber.replaceAll(/\s+/g, "");
+  const compactIban = ibanNumber.replaceAll(/\s+/g, "");
   if (!/^CH\d{19}$/.test(compactIban)) {
     return false;
   }

From 2c78286fe47132a06b20ee9017c3b60526aa08db Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Thu, 28 Aug 2025 09:03:44 +0200
Subject: [PATCH 07/11] Add the swiss IBAN to check now must be in one of the
 two defined formats

---
 src/lib/string.spec.ts |  5 +++--
 src/lib/string.ts      | 25 +++++++++++++------------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/lib/string.spec.ts b/src/lib/string.spec.ts
index e4e4d67..7fb2273 100644
--- a/src/lib/string.spec.ts
+++ b/src/lib/string.spec.ts
@@ -125,11 +125,12 @@ describe("string tests", () => {
     [null as unknown as string, false],
     [undefined as unknown as string, false],
     ["CH9300762011623852957", true],
+    ["CH93 0076 2011 6238 5295 7", true],
+    ["CH93-0076-2011-6238-5295-7", false],
     ["CH93 0000 0000 0000 0000 1", false],
     ["ch93 0076 2011 6238 5295 7", false],
     ["DE93 0076 2011 6238 5295 7", false],
-    ["CH93 0076 2011 6238 5295 7", true],
-  ])("Is Swiss IBAN valid", (unformattedIbanNumber, expected) => {
+  ])("check if this swiss IBAN is valid or not", (unformattedIbanNumber, expected) => {
     expect(isValidSwissIbanNumber(unformattedIbanNumber)).toBe(expected);
   });
 });
diff --git a/src/lib/string.ts b/src/lib/string.ts
index 3aa0315..0a3352f 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -66,27 +66,28 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
 }
 
 /**
- * Checks if the provided string is a valid Swiss IBAN number
+ * Checks if the provided string is a valid swiss IBAN number
  * @param ibanNumber The provided IBAN number to check
+ * Must be in one of the following formats:
+ * - "CHXX XXXX XXXX XXXX XXXX X" with whitespaces
+ * - "CHXXXXXXXXXXXXXXXXXXX" without whitespaces
  * @returns The result of the IBAN number check
  */
 export function isValidSwissIbanNumber(ibanNumber: string): boolean {
   if (isNullOrWhitespace(ibanNumber)) {
     return false;
   }
-  const compactIban = ibanNumber.replaceAll(/\s+/g, "");
-  if (!/^CH\d{19}$/.test(compactIban)) {
+
+  const compactIbanNumberWithWhiteSpaces = new RegExp(/^CH\d{2}(?:\s?\d{4}){4}\s?\d{1}$/);
+  const compactIbanNumberWithoutWhiteSpaces = new RegExp(/^CH\d{19}$/);
+
+  if (!compactIbanNumberWithWhiteSpaces.test(ibanNumber) && !compactIbanNumberWithoutWhiteSpaces.test(ibanNumber)) {
     return false;
   }
-  const rearrangedIban = compactIban.slice(4) + compactIban.slice(0, 4);
-  const numericStr = Array.from(rearrangedIban, (ch) => {
-    if (/[A-Z]/.test(ch)) {
-      const code = ch.codePointAt(0);
-      // code is never undefined!
-      return (code! - 55).toString();
-    }
-    return ch;
-  }).join("");
+
+  const compactInsuranceNumber = ibanNumber.replaceAll(/[\s.]+/g, "");
+  const rearrangedIban = compactInsuranceNumber.slice(4) + compactInsuranceNumber.slice(0, 4);
+  const numericStr = rearrangedIban.replaceAll(/[A-Z]/g, (ch) => (ch.codePointAt(0)! - 55).toString());
 
   let restOfCalculation = 0;
   for (const digit of numericStr) {

From 5054683531ec0f9df658195fa82cf4e0dde6da4f Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Thu, 28 Aug 2025 14:06:41 +0200
Subject: [PATCH 08/11] Removed double check

---
 src/lib/string.ts | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index 0a3352f..e8a8eb5 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -79,14 +79,13 @@ export function isValidSwissIbanNumber(ibanNumber: string): boolean {
   }
 
   const compactIbanNumberWithWhiteSpaces = new RegExp(/^CH\d{2}(?:\s?\d{4}){4}\s?\d{1}$/);
-  const compactIbanNumberWithoutWhiteSpaces = new RegExp(/^CH\d{19}$/);
 
-  if (!compactIbanNumberWithWhiteSpaces.test(ibanNumber) && !compactIbanNumberWithoutWhiteSpaces.test(ibanNumber)) {
+  if (!compactIbanNumberWithWhiteSpaces.test(ibanNumber)) {
     return false;
   }
 
-  const compactInsuranceNumber = ibanNumber.replaceAll(/[\s.]+/g, "");
-  const rearrangedIban = compactInsuranceNumber.slice(4) + compactInsuranceNumber.slice(0, 4);
+  const compactIbanNumber = ibanNumber.replaceAll(" ", "");
+  const rearrangedIban = compactIbanNumber.slice(4) + compactIbanNumber.slice(0, 4);
   const numericStr = rearrangedIban.replaceAll(/[A-Z]/g, (ch) => (ch.codePointAt(0)! - 55).toString());
 
   let restOfCalculation = 0;

From 7da0f6dbfb7ee315213d191298074051d2317c43 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Thu, 28 Aug 2025 15:22:14 +0200
Subject: [PATCH 09/11] Add explanation

---
 src/lib/string.ts | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/lib/string.ts b/src/lib/string.ts
index e8a8eb5..6729831 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -84,6 +84,19 @@ export function isValidSwissIbanNumber(ibanNumber: string): boolean {
     return false;
   }
 
+  /**
+   * Validates a Swiss IBAN number.
+   *
+   * Steps:
+   * - The number must start with `CH`, be 21 digits long and follow one of the accepted formats:
+   * - `CHXX XXXX XXXX XXXX XXXX X`or `CHXXXXXXXXXXXXXXXXXXX`.
+   * - Remove all whitespaces.
+   * - Rearrange by moving the first 4 characters (CH + 2 check digits) to the end.
+   * - Replace letters with numbers: A=10, B=11, ..., Z=35.
+   * - Convert the resulting string to a large integer and calculate modulo 97.
+   * - The number is valid if the resto of the calculation equals 1.
+   */
+
   const compactIbanNumber = ibanNumber.replaceAll(" ", "");
   const rearrangedIban = compactIbanNumber.slice(4) + compactIbanNumber.slice(0, 4);
   const numericStr = rearrangedIban.replaceAll(/[A-Z]/g, (ch) => (ch.codePointAt(0)! - 55).toString());

From 42ce69d46cf153f9592ccafdf85d55903015bcde Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Tue, 2 Sep 2025 16:56:43 +0200
Subject: [PATCH 10/11] Add double regex schema for IBAN number check

---
 src/lib/string.spec.ts |  1 +
 src/lib/string.ts      | 31 ++++++++++++++++---------------
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/lib/string.spec.ts b/src/lib/string.spec.ts
index 7fb2273..f9c167e 100644
--- a/src/lib/string.spec.ts
+++ b/src/lib/string.spec.ts
@@ -126,6 +126,7 @@ describe("string tests", () => {
     [undefined as unknown as string, false],
     ["CH9300762011623852957", true],
     ["CH93 0076 2011 6238 5295 7", true],
+    ["CH930076 20116238 5295 7", false],
     ["CH93-0076-2011-6238-5295-7", false],
     ["CH93 0000 0000 0000 0000 1", false],
     ["ch93 0076 2011 6238 5295 7", false],
diff --git a/src/lib/string.ts b/src/lib/string.ts
index 6729831..5215667 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -74,37 +74,38 @@ export function truncate(value: string | undefined, maxLength: number, suffix =
  * @returns The result of the IBAN number check
  */
 export function isValidSwissIbanNumber(ibanNumber: string): boolean {
+  // 1. Reject null, undefined or whitespace-only strings
   if (isNullOrWhitespace(ibanNumber)) {
     return false;
   }
 
-  const compactIbanNumberWithWhiteSpaces = new RegExp(/^CH\d{2}(?:\s?\d{4}){4}\s?\d{1}$/);
+  // 2. Define allowed strict formats
+  //    - with spaces: "CHXX XXXX XXXX XXXX XXXX X"
+  const compactIbanNumberWithWhiteSpaces = new RegExp(/^CH\d{2}(?: \d{4}){4} \d{1}$/);
+  //    - without spaces: "CHXXXXXXXXXXXXXXXXXXX"
+  const compactIbanNumberWithoutWhiteSpaces = new RegExp(/^CH\d{19}$/);
 
-  if (!compactIbanNumberWithWhiteSpaces.test(ibanNumber)) {
+  // 3. Check if input matches one of the allowed formats
+  if (!compactIbanNumberWithWhiteSpaces.test(ibanNumber) && !compactIbanNumberWithoutWhiteSpaces.test(ibanNumber)) {
     return false;
   }
 
-  /**
-   * Validates a Swiss IBAN number.
-   *
-   * Steps:
-   * - The number must start with `CH`, be 21 digits long and follow one of the accepted formats:
-   * - `CHXX XXXX XXXX XXXX XXXX X`or `CHXXXXXXXXXXXXXXXXXXX`.
-   * - Remove all whitespaces.
-   * - Rearrange by moving the first 4 characters (CH + 2 check digits) to the end.
-   * - Replace letters with numbers: A=10, B=11, ..., Z=35.
-   * - Convert the resulting string to a large integer and calculate modulo 97.
-   * - The number is valid if the resto of the calculation equals 1.
-   */
-
+  // 4. Remove all spaces to get a compact IBAN string
   const compactIbanNumber = ibanNumber.replaceAll(" ", "");
+
+  // 5. Rearrange IBAN for checksum calculation
+  //    - move first 4 characters (CH + 2 check digits) to the end
   const rearrangedIban = compactIbanNumber.slice(4) + compactIbanNumber.slice(0, 4);
+
+  // 6. Replace letters with numbers (A=10, B=11, ..., Z=35)
   const numericStr = rearrangedIban.replaceAll(/[A-Z]/g, (ch) => (ch.codePointAt(0)! - 55).toString());
 
+  // 7. Perform modulo 97 calculation to validate IBAN
   let restOfCalculation = 0;
   for (const digit of numericStr) {
     restOfCalculation = (restOfCalculation * 10 + Number(digit)) % 97;
   }
 
+  // 8. IBAN is valid only if the remainder equals 1
   return restOfCalculation === 1;
 }

From 328ef6c84570ee959ce9ffa76dcbb2198f98aa76 Mon Sep 17 00:00:00 2001
From: Dominic Baur <dominic.baur@collana.com>
Date: Wed, 3 Sep 2025 15:16:13 +0200
Subject: [PATCH 11/11] Formatted

---
 src/lib/string.spec.ts | 14 +++++++++++---
 src/lib/string.ts      |  2 +-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/lib/string.spec.ts b/src/lib/string.spec.ts
index f18d05a..2c0d975 100644
--- a/src/lib/string.spec.ts
+++ b/src/lib/string.spec.ts
@@ -1,4 +1,12 @@
-import { isNullOrEmpty, isNullOrWhitespace, capitalize, uncapitalize, truncate, isValidSwissIbanNumber ,isValidSwissSocialSecurityNumber } from "./string";
+import {
+  isNullOrEmpty,
+  isNullOrWhitespace,
+  capitalize,
+  uncapitalize,
+  truncate,
+  isValidSwissIbanNumber,
+  isValidSwissSocialSecurityNumber,
+} from "./string";
 
 describe("string tests", () => {
   test.each([
@@ -134,7 +142,7 @@ describe("string tests", () => {
   ])("check if this swiss IBAN is valid or not", (unformattedIbanNumber, expected) => {
     expect(isValidSwissIbanNumber(unformattedIbanNumber)).toBe(expected);
   });
-  
+
   test.each([
     [null as unknown as string, false],
     [undefined as unknown as string, false],
@@ -149,4 +157,4 @@ describe("string tests", () => {
   ])("check if the social insurance number is valid or not", (ahvNumber, expected) => {
     expect(isValidSwissSocialSecurityNumber(ahvNumber)).toBe(expected);
   });
-});
\ No newline at end of file
+});
diff --git a/src/lib/string.ts b/src/lib/string.ts
index c0aa095..c8fbdcb 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -171,4 +171,4 @@ export function isValidSwissSocialSecurityNumber(socialInsuranceNumber: string):
    *    - If equal → valid AHV number
    */
   return checksum === checknumber;
-}
\ No newline at end of file
+}