Calculate word frequency

word-freq.js

// source: https://blog.heroku.com/kafka-data-pipelines-frp-node?c=7013A000000tyBBQAY&utm_campaign=Newsletter_December_2016&utm_medium=email&utm_source=newsletter&utm_content=blog&utm_term=kafka-data-pipelines-frp-node
function wordFreq(accumulator, string) {
  return _.replace(string, /[\.!\?"'#,\(\):;-]/g, '') //remove special characters
    .split(/\s/)
    .map(word => word.toLowerCase())
    .filter(word => ( !_.includes(stopWords, word) )) //dump words in stop list
    .filter(word => ( word.match(/.{2,}/) )) //dump single char words
    .filter(word => ( !word.match(/\d+/) )) //dump all numeric words
    .filter(word => ( !word.match(/http/) )) //dump words containing http
    .filter(word => ( !word.match(/@/) )) //dump words containing @
    .reduce((map, word) =>
      Object.assign(map, {
        [word]: (map[word]) ? map[word] + 1 : 1,
      }), accumulator
    )
}