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      • New Set methods S4

      Proposal details
      Proposal overview

      This proposal adds set operation methods like union, intersection, and difference to JavaScript's built-in Set prototype, solving the need for common set operations without third-party libraries. It specifies seven methods, all requiring arguments that have a numeric size property and keys and has methods.

      Note

      The README below comes from the upstream repository and may contain outdated stage or status metadata. Use the proposal details above as the current source of truth.

      Set Methods for JavaScript

      This is a proposal to add methods like union and intersection to JavaScript's built-in Set class.

      It is currently at stage 4: it has been added to the specification. This repository is no longer active.

      Original readme follows.

      Proposal

      This would add the following methods:

      • Set.prototype.intersection(other)
      • Set.prototype.union(other)
      • Set.prototype.difference(other)
      • Set.prototype.symmetricDifference(other)
      • Set.prototype.isSubsetOf(other)
      • Set.prototype.isSupersetOf(other)
      • Set.prototype.isDisjointFrom(other)

      These methods would all require their arguments to be a Set, or at least something which looks like a Set in terms of having a numeric size property as well as keys and has methods.

      See details.md for details of current decisions made in this proposal.

      Rendered spec text is available here.

      The proposal was originally authored by Michał Wadas and later championed by Sathya Gunasekaran and Kevin Gibbons.

      Implementations

      This proposal is ready for engines to implement and ship. See this issue for current status.

      TC39 meeting notes

      (Semi)relevant previous discussions

      Comparison with other languages

      See other languages document to get overview of Set methods in other languages.

      Naming

      See naming bikeshedding document for details.

      We decided to choose:

      • Symmetric difference - symmetricDifference
      • Intersection - intersection
      • Union - union
      • Difference - difference

      Polyfills