How to use

flatMap

function

in

Stream

_(readDir(linksPath))
  .map(arr => arr.sort((a, b) => a.localeCompare(b)))
  .flatMap(arr => _(arrayMod(arr)))
  .flatMap(filepath => exports.fileToContent(filepath, linksPath))
  .flatMap(file => exports.fileToDocuments(file))

.filter(section => section && section.length > 0 && section.replace(/\n/g, '').length > 0)
.map(text => ({text, filename}))
.flatMap(({text, filename}) => {
 const [, episodeName] = /\d+-\d+-(.+?)\./.exec(filename);
 const [name, linksText] = text.split(/:\n/g);

let shouldThrow = false;
const res = await fileToContent(lastFile, linksPath)
 .flatMap(content => fileToDocuments(content))
 .flatMap(doc => {
  const titleRes = findInTitles(doc.title, index);
  const urlsRes = findInUrls(doc.urls, index);