JS Built-ins
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ObjectObject.groupByintermediate

Object.groupBy() — group by first letter

📖 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() — string key derived from item

You can derive the group key from any property of the item. Grouping words by their first letter is a natural example.

Challenge: Implement groupByFirstLetter(words) that groups words by their first character.

groupByFirstLetter(['apple', 'ant', 'banana'])
// → { a: ['apple', 'ant'], b: ['banana'] }
💡 Hints (1)
  • • Return `w[0]` (or `w.charAt(0)`) from the key function.