README.md in trackler-2.2.1.95

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-# ISBN Verifier
+# Isbn Verifier
 
-Check if a given ISBN-10 is valid.
+The [ISBN-10 verification process](https://en.wikipedia.org/wiki/International_Standard_Book_Number) is used to validate book identification
+numbers. These normally contain dashes and look like: `3-598-21508-8`
 
-## Functionality
+## ISBN
 
-Given an unknown string the program should check if the provided string is a valid ISBN-10.
-Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
+The ISBN-10 format is 9 digits (0 to 9) plus one check character (either a digit or an X only). In the case the check character is an X, this represents the value '10'. These may be communicated with or without hyphens, and can be checked for their validity by the following formula:
 
-The program should allow for ISBN-10 without the separating dashes to be verified as well.
+```
+(x1 * 10 + x2 * 9 + x3 * 8 + x4 * 7 + x5 * 6 + x6 * 5 + x7 * 4 + x8 * 3 + x9 * 2 + x10 * 1) mod 11 == 0
+```
 
-## ISBN
+If the result is 0, then it is a valid ISBN-10, otherwise it is invalid.
 
-Let's take a random ISBN-10 number, say `3-598-21508-8` for this.
-The first digit block indicates the group where the ISBN belongs. Groups can consist of shared languages, geographic regions or countries. The leading '3' signals this ISBN is from a german speaking country.
-The following number block is to identify the publisher. Since this is a three digit publisher number there is a 5 digit title number for this book.
-The last digit in the ISBN is the check digit which is used to detect read errors.
+## Example
 
-The first 9 digits in the ISBN have to be between 0 and 9.
-The check digit can additionally be an 'X' to allow 10 to be a valid check digit as well.
+Let's take the ISBN-10 `3-598-21508-8`. We plug it in to the formula, and get:
+```
+(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 == 0
+```
 
-A valid ISBN-10 is calculated with this formula `(x1 * 10 + x2 * 9 + x3 * 8 + x4 * 7 + x5 * 6 + x6 * 5 + x7 * 4 + x8 * 3 + x9 * 2 + x10 * 1) mod 11 == 0`
-So for our example ISBN this means:
-(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 = 0
+Since the result is 0, this proves that our ISBN is valid.
 
-Which proves that the ISBN is valid.
+## Task
 
-## Setup
+Given a string the program should check if the provided string is a valid ISBN-10.
+Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
 
-Go through the setup instructions for JavaScript to
-install the necessary dependencies:
+The program should be able to verify ISBN-10 both with and without separating dashes.
 
-http://exercism.io/languages/javascript
 
-## Making the Test Suite Pass
+## Caveats
 
-Execute the tests with:
+Converting from strings to numbers can be tricky in certain languages.
+Now, it's even trickier since the check digit of an ISBN-10 may be 'X' (representing '10'). For instance `3-598-21507-X` is a valid ISBN-10.
 
-    jasmine <exercise-name>.spec.js
+## Bonus tasks
 
-Replace `<exercise-name>` with the name of the current exercise. E.g., to
-test the Hello World exercise:
+* Generate a valid ISBN-13 from the input ISBN-10 (and maybe verify it again with a derived verifier).
 
-    jasmine hello-world.spec.js
+* Generate valid ISBN, maybe even from a given starting ISBN.
+## Setup
 
-In many test suites all but the first test have been skipped.
+Go through the setup instructions for JavaScript to install the
+ necessary dependencies:
 
-Once you get a test passing, you can unskip the next one by
-changing `xit` to `it`.
+http://exercism.io/languages/javascript/installation
 
-### Submitting Exercises
+## Running the test suite
 
-Note that, when trying to submit an exercise, make sure the solution is in the `exercism/javascript/<exerciseName>` directory.
+The provided test suite uses [Jasmine](https://jasmine.github.io/).
+You can install it by opening a terminal window and running the
+following command:
 
-For example, if you're submitting `bob.js` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/javascript/bob/bob.js`.
+```sh
+npm install -g jasmine
+```
 
+Run the test suite from the exercise directory with:
 
-For more detailed information about running tests, code style and linting,
-please see the [help page](http://exercism.io/languages/javascript).
+```sh
+jasmine isbn-verifier.spec.js
+```
 
+In many test suites all but the first test have been marked "pending".
+Once you get a test passing, activate the next one by changing `xit` to `it`.
+
 ## Source
 
-Converting a string into a number and some basic processing utilizing a relatable real world example. [https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation](https://en.wikipedia.org/wiki/International_Standard_Book_Number)
+Converting a string into a number and some basic processing utilizing a relatable real world example. [https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation](https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation)
 
 ## Submitting Incomplete Solutions
 It's possible to submit an incomplete solution so you can see how others have completed the exercise.