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Group By

EasyP2Coding

Implement groupBy(items, iteratee), which groups the elements of an array by a key.

  • iteratee is either a function, called with each element to get its key, or a string naming a property to read from each element.
  • Return an object whose keys are the group keys (converted to strings, as object keys always are) and whose values are arrays of the elements in that group, in their original order.
  • An empty input returns {}. The input array is not modified.

Example 1

Input
groupBy([6.1, 4.2, 6.3], Math.floor)
Output
{ '4': [4.2], '6': [6.1, 6.3] }

Example 2

Input
groupBy([{t:'a'},{t:'b'},{t:'a'}], 't')
Output
{ a: [{t:'a'},{t:'a'}], b: [{t:'b'}] }

Constraints

  • 0 <= items.length <= 10^5

Hints

Run checks the 3 visible tests, Submit all 8.