Decimal-to-roman-converter NPM

Decimal to Roman Numerals Converter

Convert any decimal integer from 1 - 3999 to the equivalent roman numeral.

$ npm install

Run:

$ npm test

$ npm install --save decimal-to-roman-converter

To use:

const generator = require('decimal-to-roman-converter');
generator(3999);

First step in creating the generator was to understand all the possible decimal - roman translations.
Although there is only 7 distinct roman symbols, given the subtractive pattern that is used, it would mean a total of 13 different translations were possible:

Each decimal - roman translation were separated into their own object for easily accessing the values later.
They were then put into an array from highest - lowest decimal value.
The order of the array is crucial given that roman numerals read from left - right the same as decimal values.
To actually generate the roman numeral is a simple process:
- Loop through the translations array.
- While the supplied number is greater than or equal to that index's decimal value then:
  - Append the roman value to the conversion string.
  - Then subtract the decimal value from the supplied number.
- If the supplied number is less than the index's decimal value then move to the next index in the array.
- Finally once the array has been looped through return the generated roman conversion.

To make the function robust there are two custom error objects created to effectively handle wrong inputs:
- If the input is not a number (in JavaScript terms) it will throw a NotNumberException
- If the input is a number but not within the range 1 - 3999 (the general limit for roman numerals) or is not a valid nteger then it will throw a NotValidIntegerException
Returning custom errors will mean the user will have a good understanding of why their input is wrong
All the error handling is done at the start of the function to stop any unecessary code executing.

The jest package was installed as the testing framework - it allows you to create tests that output human readable test cases.
Instead of testing all possible values from 1 - 3999 only a selected set of test cases were included:
- As set of simple values to prove the generator was working.
- A set of more complicated numbers that tested the generator was handling the subtractive pattern correctly.
- A set of non-valid integers to make sure the proper error was returned.
- A set of values that were not a number to make sure the proper error was returned.

Without testing all the integers from 1 - 3999 it is assumed that the limited test case is sufficient to prove functionality.
It is assumed that a test case that makes most use of the subtractive pattern is the most likely, if any, to be wrong given that it uses the subtractive pattern.

Martin Bolton MacDonald

5 years ago

5 years ago