refactoring challenge from @airporty => https://twitter.com/airportyh/status/931540087602581504

example-refactored.js

// 17 November 2017
// original https://gist.github.com/airportyh/203f7c2d8a8b29af44218b79596af32f
// from @airporty https://twitter.com/airportyh/status/931540087602581504

// The initial refactoring breaks `main()` steps to smaller functions, but adds
// whitespace.

// 21 November 2017 - added discrete unit tests for each function, vastly more
// robust, heavily renamed, heavier on comments.

// 4 Jan 2018 - more method renaming.

function getPluralFor(number) {
  // simplified by unit test - accept only number or coercible param
  return Number(number) === 1  ? '' : 's'
}

function getNameFor(author) {
  // fixed by unit test with trim()
  var name = (author.name || '').trim()
  
  return name
    || [author.firstName, author.lastName]
        .join(' ')
        .replace(/'/g, '')
        .trim()
    || '<Unknown author>'
}

function getArticlesBy(author) {
  var articles = author.articles;
  
  return Array.isArray(articles) ? articles : []
}

function getTitleFor(article) {
  // fixed by unit test with article and title.trim()
  var title = article.title
  
  return typeof title == 'string' && title.trim() || '<Untitled>'
}

function useLettersAndDigits(word) {
  return word.replace(/[^\d^\w]/g, '')
}

function isNonEmpty(word) {
  // filter added by unit test
  var length = typeof word == 'string' ? word.trim().length : 0
  
  return !!length
}

function getWordcountFor(article) {
  // type check added by unit tests
  contents = article && typeof article.contents == 'string' ? article.contents.trim() : ''
  
  // filter added by unit test
  var words = contents
    .split(/[\s]+/)
    .map(useLettersAndDigits)
    .filter(isNonEmpty);
    
  var set = new Set(words)

  // return check fixed by unit tests
  // if words.length is 0, return 0
  // else return size of unique set
  return words.length && set.size
}

function forEachArticle(article) {
  // fixed by unit testing
  var title = getTitleFor(article)
  var wordCount = getWordcountFor(article)
  
  return { title, wordCount }
}

function forEachTitle(article) {
  // title fixed by unit testing
  var title = getTitleFor(article)
  var wordCount = article.wordCount
  var plural = getPluralFor(wordCount)

  return `  Article "${title}" has ${wordCount} unique word${plural}.`
}

function forEachAuthor(author) {
  // default check added by unit tests
  if (author == null) {
    return undefined
  }
  
  var name = getNameFor(author)
  var articles = getArticlesBy(author)
  var articleCount = articles.length
  var plural = getPluralFor(articleCount)
  
  var aboutAuthor = `Author "${name}" has published ${articleCount} article${plural}.`
  var aboutTitles = articles
    .map(forEachArticle)
    .map(forEachTitle)
  
  return {
    author: aboutAuthor,
    titles: aboutTitles
  }
}

/* entry point */

function main(authors) {
  if (!Array.isArray(authors) || !authors.length) {
    return
  }
  
  authors.map(forEachAuthor).map(about => {
    console.warn(about.author)

    about.titles.map(function(title) {
      console.log(title)
    })
  })
}


/* test it out */

console.info("/* main api test */")

var fixture = [
  { name: 'test'},
  { firstName: 'firsty'},
  { firstName: 'firsty', lastName: 'lasty'},
  { name: 'namey', firstName: 'firsty', lastName: 'lasty'},
  { articles: []},
  { articles: [{ title: 'short Title'}]},
  { articles: [{ title: '', contents: "not a very long article"}]},
  { name: 'some author', articles: [{ title: 'some title', contents: "some contents containing 5 words."}]},
  {
    firstName: 'Author', lastName: 'McAuthor',
    articles: [
      {
        title: 'Interesting Book with Words',
        contents: "I found this book so awesome I can't hardly read it anymore, full stop."
      },
      {
        title: 'Rex Tillerson\'s Guide to the Department of State',
        contents: "I found this book really awesome and I couldn't put it down after 10.5 minutes."
      },
      {
        title: 'Lance Shmendrickson',
        contents: "Nothing but numbers like, 8, 8, and 8."
      }
    ]
  }

]

/* call it */

main(fixture)

// Should see =>
/*
  Author "test" has published 0 articles.
  Author "firsty" has published 0 articles.
  Author "firsty lasty" has published 0 articles.
  Author "namey" has published 0 articles.
  Author "<Unknown author>" has published 0 articles.
  Author "<Unknown author>" has published 1 article.
    Article "short Title" has 0 unique words.
  Author "<Unknown author>" has published 1 article.
    Article "<Untitled>" has 5 unique words.
  Author "some author" has published 1 article.
    Article "some title" has 5 unique words.
  Author "Author McAuthor" has published 3 articles.
    Article "Interesting Book with Words" has 13 unique words.
    Article "Rex Tillerson's Guide to the Department of State" has 14 unique words.
    Article "Lance Shmendrickson" has 6 unique words.
 */


/* unit tests */

console.log("\n")
console.info("/* unit tests */")
console.info("assertions should print test title followed by")
console.info("%c true", 'color: blue')

console.log("expect getPluralFor('3') to return 's'",
  getPluralFor('3') === 's')
console.log("expect getPluralFor(1) to return ''",
  getPluralFor(1) === '')
console.log("expect getPluralFor(-2) to return 's'",
  getPluralFor(-2) === 's') // pathological test

console.log("expect getNameFor({ name: 'james' }) to return 'james'",
  getNameFor({ name: 'james' }) === 'james')
console.log("expect getNameFor({ name: 'james', lastName: 'last' }) to return only 'james'",
  getNameFor({ name: 'james', lastName: 'last' }) === 'james')
console.log("expect getNameFor({ firstName: 'james', lastName: 'last' }) to return 'james last'",
  getNameFor({ firstName: 'james', lastName: 'last' }) === 'james last')
console.log("expect getNameFor({ name: ' ', firstName: ' ', lastName: ' ' }) to return '<Unknown author>'",
  getNameFor({ name: ' ', firstName: ' ', lastName: ' ' }) === '<Unknown author>')

console.log("expect getNameFor({ }) to return empty array",
  getNameFor({ }).length === 0)
console.log("expect getNameFor({ articles: { one: 'one article' } }) to return empty array",
  getNameFor({ articles: { one: 'one article' } }).length === 0)
console.log("expect getNameFor({ articles: [{ title: 'one article' }] }) to return array of one item",
  getNameFor({ articles: [{ title: 'one article' } ] })[0].title === 'one article')

console.log("expect getTitleFor({ title: 'one article' }) to return 'one article'",
  getTitleFor({ title: 'one article' }) === 'one article')
console.log("expect getTitleFor({ title: ' ' }) to return '<Untitled>'",
  getTitleFor({ title: ' ' }) === '<Untitled>')

console.log("expect useLettersAndDigits('123.456') to return '123456'",
  useLettersAndDigits('123.456') === '123456')
console.log("expect useLettersAndDigits('comma,') to return 'comma'",
  useLettersAndDigits('comma,') === 'comma')  
console.log("expect useLettersAndDigits('1for2') to return '1for2'",
  useLettersAndDigits('1for2') === '1for2')
console.log("expect useLettersAndDigits('self-regard') to return 'selfregard'",
  useLettersAndDigits('self-regard') === 'selfregard')
console.log("expect useLettersAndDigits('') to return ''",
  useLettersAndDigits('') === '')

console.log("expect isNonEmpty(' ') to return false",
  isNonEmpty(' ') === false)
console.log("expect isNonEmpty(' 5 ') to return true",
  isNonEmpty(' 5 ') === true)

console.log("expect getWordcountFor({ contents: 'one one' }) to return 1",
  getWordcountFor({ contents: 'one one' }) === 1)
console.log("expect getWordcountFor({ contents: ' ' }) to return 0",
  getWordcountFor({ contents: ' ' }) === 0)
console.log("expect getWordcountFor({ contents: ' h red 99 ' }) to return 3",
  getWordcountFor({ contents: ' h red 99 ' }) === 3)

console.log("expect forEachArticle({ title: 'test' }).title to return 'test'",
  forEachArticle({ title: 'test' }).title === 'test')
console.log("expect forEachArticle({ contents: 'testing one two three and three only ' }).wordCount to return 6",
  forEachArticle({ contents: 'testing one two three and three only ' }).wordCount === 6)

console.log("expect forEachTitle({ title: 'test', wordCount: 3 }) to return \"  Article \"test\" has 3 unique words.\"",
  forEachTitle({ title: 'test', wordCount: 3 }) === "  Article \"test\" has 3 unique words.")
console.log("expect forEachTitle({ wordCount: 1 }) to return \"  Article \"<Untitled>\" has 1 unique word.\"",
  forEachTitle({ wordCount: 1 }) === "  Article \"<Untitled>\" has 1 unique word.")

console.log("expect forEachAuthor() to return undefined",
  forEachAuthor() === undefined)
console.log("expect forEachAuthor({ articles: [1,2,3] }).author to return \"Author \"<Unknown author>\" has published 3 articles.\"",
  forEachAuthor({ articles: [1,2,3] }).author === "Author \"<Unknown author>\" has published 3 articles.")
console.log("expect forEachAuthor({ firstName: 'Ted', lastName: 'Johanson', articles: [8] }).author to return \"Author \"Ted Johanson\" has published 1 article.\"",
  forEachAuthor({ firstName: 'Ted', lastName: 'Johanson', articles: [8] }).author === "Author \"Ted Johanson\" has published 1 article.")

example.js

// original from @airporty
// gist https://gist.github.com/airportyh/203f7c2d8a8b29af44218b79596af32f
// tweet https://twitter.com/airportyh/status/931540087602581504

function main(authors) {
  authors.forEach(function(author) {
    let name, articles;
    if (author) {
      if (author.name) {
        name = author.name;
      } else if (author.firstName) {
        if (author.lastName) {
          name = author.firstName + ' ' + author.lastName;
        } else {
          name = author.firstName;
        }
      }
    }
    if (!name) {
      name = '<Unknown author>';
    }
    if (author) {
      articles = author.articles;
    }
    if (!articles) {
      articles = [];
    }
    let articleCount = articles.length;
    let maybeS = articleCount > 1 || articleCount === 0  ? 's' : '';
    console.log(`${name} has published ${articles.length} article${maybeS}.`);
    articles.forEach(function(article) {
      let title, wordCount;
      if (article) {
        title = article.title;
      }
      if (!title) {
        title = '<Untitled>';
      }
      if (article) {
        if (article.contents) {
          let words = article.contents
            .split(/[^A-Za-z']+/)
            .filter(word => !!word);
          wordCount = words.length;
        }
      }
      if (!wordCount) {
        wordCount = 0;
      }
      console.log(`  Article ${title} has ${wordCount} words.`);
    });
  });
}