So, whilst Sets were a great addition to JavaScript, there did seem to be some glaring omissions. The most obvious of these were the basic set operations: union, intersection, and difference.
We can easily add these with Metho:
import * as metho from "metho" const target = Set.prototype export const union = Metho.add( target, function(set) { return new Set([...this, ...set]) } ) export const intersect = Metho.add( target, function(set) { return new Set([...this].filter(i=>set.has(i))) } ) export const difference = Metho.add( target, function(set) { return new Set([...this].filter(i=>!set.has(i))) } ) const a = new Set([1, 2, 3]) const b = new Set([3, 4, 5]) // everything from both sets console.log( a[union(b)] ) // Set(5)[ 1, 2, 3, 4, 5 ] // everything that exists in both set a and set b console.log( a[intersect(b)] ) // Set [ 3 ] // everything that exists in set a, but not in set b console.log( a[difference(b)] ) // Set [ 1, 2 ] I have made these extensions available in the metho-set library
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