Fix problem with friendlyFormatIBAN and invalid argument

ChangeLog

@@ -1,8 +1,9 @@
 2019-05-05  Saša Jovanić  <sasa@simplify.ba>
-	* Merged PR1 - Renamed `main:jsnext` to `modules` - Thanks @NeoLegends
+	* Merged PR1 - Renamed `main:jsnext` to `modules` - Thanks @NeoLegends ()PR1/GH9)
 	* Upraded various packages containing security vulnerabilities using `npm audit fix`
 	* Upgraded Gulp to version 4 and all gulp tasks
 	* Added Vatican City State
+	* `friendlyFormatIBAN` and `electronicFormatIBAN` will return `null` when non-string value is provided (GH15).
 
 2018-03-11  Saša Jovanić  <sasa@simplify.ba>
 	* Released version 2.0.0

src/IBANTools.ts

@@ -144,6 +144,7 @@ function checkFormatBBAN(bban: string, bformat: string): boolean {
 /**
  * Get IBAN in electronic format (no spaces)
  * IBAN validation is not performed.
+ * When non-string value for IBAN is provided, returns null.
  * @example
  * // returns "NL91ABNA0417164300"
  * ibantools.electronicFormatIBAN("NL91 ABNA 0417 1643 00");
@@ -152,15 +153,14 @@ function checkFormatBBAN(bban: string, bformat: string): boolean {
  * @return {string} IBAN Electronic formated IBAN
  */
 export function electronicFormatIBAN(iban: string) {
-  if (iban === undefined || iban === null) {
-    return null;
-  }
+  if (typeof iban !== "string") { return null; }
   return iban.replace(/[-\ ]/g, "").toUpperCase();
 }
 
 /**
  * Get IBAN in friendly format (separated after every 4 characters)
  * IBAN validation is not performed.
+ * When non-string value for IBAN is provided, returns null.
  * @example
  * // returns "NL91 ABNA 0417 1643 00"
  * ibantools.friendlyFormatIBAN("NL91ABNA0417164300");
@@ -173,6 +173,7 @@ export function electronicFormatIBAN(iban: string) {
  * @return {string} IBAN Friendly formated IBAN
  */
 export function friendlyFormatIBAN(iban: string, separator?: string) {
+  if (typeof iban !== "string") { return null; }
   if (typeof separator === "undefined") { separator = " "; }
   return electronicFormatIBAN(iban).replace(/(.{4})(?!$)/g, "$1" + separator);
 }

test/IBANToolsTest.ts

@@ -281,6 +281,15 @@ describe("IBANTools", () => {
     });
   });
 
+  describe("When calling friendlyFormatIBAN() with invalid argument", () => {
+    it("returns null when undefined is provided", () => {
+      expect(iban.friendlyFormatIBAN(undefined)).to.be.null;
+    });
+    it("returns null when null is provided", () => {
+      expect(iban.friendlyFormatIBAN(null)).to.be.null;
+    });
+  });
+
   describe("When calling getCountrySpecifications()", () => {
     const ext = iban.getCountrySpecifications();
     it("Country with code NL should return name Netherlands", () => {