Get all files within a directory (deep/recursive) using the web File System Access API

crawlDirectory.js

async function crawlDirectory(directoryHandle, files) {
  for await (let [name, handle] of directoryHandle.entries()) {
    if(handle.kind === "file") files.push(handle);
    else if(handle.kind === "directory") crawlDirectory(handle, files);
  }
}

let directoryHandle = await window.showDirectoryPicker();
let files = [];
await crawlDirectory(directoryHandle, files);

// Example to show how to use the file handles (we count hyphenated words):
let hyphenatedWordsHist = {};
for(let fileHandle of files) {
  let file = await fileHandle.getFile();
  let text = await file.text();
  let hyphenatedWords = [...text.toLowerCase().matchAll(/\s([a-z]+-[a-z]+)[\s?!.]/g)].map(m => m[1]);
  hyphenatedWords.forEach(w => hyphenatedWordsHist[w] = (hyphenatedWordsHist[w] || 0) + 1);
}

let top1000HyphenatedWords = Object.entries(hyphenatedWordsHist).sort((a,b) => b[1]-a[1]).slice(0, 1000);