JS Built-ins
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ObjectObject.groupByintermediate

Object.groupBy() — group strings by length

📖 Usage Example
// Group array items by a computed key
const items = [{ type: 'a', v: 1 }, { type: 'b', v: 2 }, { type: 'a', v: 3 }]
Object.groupBy(items, item => item.type)
// → { a: [{...}, {...}], b: [{...}] }

Use Object.groupBy() to group an array's elements into an object keyed by a value returned from a callback.

Object.groupBy() — numeric group keys

The key function can return a number too (it gets coerced to a string key). Grouping strings by length is a common example.

Challenge: Implement groupByLength(words) that groups strings by their .length.

groupByLength(['a', 'bb', 'cc', 'ddd'])
// → { '1': ['a'], '2': ['bb', 'cc'], '3': ['ddd'] }
💡 Hints (1)
  • • Return `w.length` from the key function — numbers are coerced to string keys.