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4d47's solution

to RNA Transcription in the JavaScript Track

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Instructions
Test suite
Solution

Given a DNA strand, return its RNA complement (per RNA transcription).

Both DNA and RNA strands are a sequence of nucleotides.

The four nucleotides found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).

The four nucleotides found in RNA are adenine (A), cytosine (C), guanine (G) and uracil (U).

Given a DNA strand, its transcribed RNA strand is formed by replacing each nucleotide with its complement:

  • G -> C
  • C -> G
  • T -> A
  • A -> U

Setup

Go through the setup instructions for Javascript to install the necessary dependencies:

https://exercism.io/tracks/javascript/installation

Requirements

Install assignment dependencies:

$ npm install

Making the test suite pass

Execute the tests with:

$ npm test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing xtest to test.

Source

Hyperphysics http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/transcription.html

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

rna-transcription.spec.js

import { toRna } from './rna-transcription';

describe('Transcriptor', () => {

  test('empty rna sequence', () => {
    expect(toRna('')).toEqual('');
  });

  xtest('transcribes cytosine to guanine', () => {
    expect(toRna('C')).toEqual('G');
  });

  xtest('transcribes guanine to cytosine', () => {
    expect(toRna('G')).toEqual('C');
  });

  xtest('transcribes adenine to uracil', () => {
    expect(toRna('A')).toEqual('U');
  });

  xtest('transcribes thymine to adenine', () => {
    expect(toRna('T')).toEqual('A');
  });

  xtest('transcribes all dna nucleotides to their rna complements', () => {
    expect(toRna('ACGTGGTCTTAA'))
        .toEqual('UGCACCAGAAUU');
  });

  xtest('correctly handles invalid input', () => {
    expect(() => toRna('U')).toThrow(
      new Error('Invalid input DNA.'),
    );
  });

  xtest('correctly handles completely invalid input', () => {
    expect(() => toRna('XXX')).toThrow(
      new Error('Invalid input DNA.'),
    );
  });

  xtest('correctly handles partially invalid input', () => {
    expect(() => toRna('ACGTXXXCTTAA')).toThrow(
      new Error('Invalid input DNA.'),
    );
  });
});
export default class {
  constructor(complements = { G: 'C', C: 'G', T: 'A', A: 'U'}) {
    this.complements = complements
  }

  toRna(s) {
    return [...s].map(c => this.transcript(c)).join('')
  }

  transcript(c) {
    if (c = this.complements[c])
      return c
    throw Error('Invalid input DNA.')
  }
}

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?