Array.fromAsync & Grouping in JavaScript

// Array.fromAsync — collect an async iterable into an array
async function* lines(file) {
  for await (const chunk of file.stream()) yield chunk
}
const allLines = await Array.fromAsync(lines(myFile))

// Object.groupBy — group items by a derived key (ES2024)
const items = [
  { name: 'apple', type: 'fruit' },
  { name: 'carrot', type: 'veg' },
  { name: 'pear', type: 'fruit' },
]
const byType = Object.groupBy(items, x => x.type)
// { fruit: [{...apple}, {...pear}], veg: [{...carrot}] }

// Map.groupBy — same idea, but the key can be any value (incl. objects)
const byParent = Map.groupBy(rows, r => r.parent)