If I have an array of Sets, what is the best method to combine these Sets into a single Set?
Say if I had this array:
const array = [new Set([1, 2, 3]), new Set([4, 5, 6]), new Set([7, 8, 9])]
How would I manipulate this array in order to produce a single Set with the same output as:
new Set([1,2,3,4,5,6,7,8,9])
This array has an arbitrary number of sets of arbitrary size.
You can also use reduce
new Set( array.reduce( ( a, c ) => a.concat( [...c] ), [] ) )
Demo
var array = [new Set([1, 2, 3]), new Set([4, 5, 6]), new Set([7, 8, 9])];
var output = new Set( array.reduce( ( a, c ) => a.concat( [...c] ), [] ) );
console.log( [...output] );
Set and it will eliminate all duplicate entries anyways.
c is a Set. Spreading it does not make a difference.
[...output] is actually converting the Set into an array. You could iterate over the set keys() or values() but it's easier to convert it into to array an console output itThe simplest is the best:
let result = new Set;
for (const set of array)
for (const element of set)
result.add(element);
Alternatively, if you want to use the constructor, I'd go for an immediately invoked generator function to create an iterator:
const result = new Set(function* () {
for (const set of array)
yield* set;
}());
Of course you can also declare a reusable functional-minded generator function for this:
function* flatten(iterable) {
for (const inner of iterable)
for (const element of inner)
yield element;
}
const result = new Set(flatten(array));
new Set([...array[0], ...array[1], ...array[2]])?new Set(...array), but it only expands the first Set. I tried using the spread operator within array.map, but kept running into issues.new Set(array.map(set => ...set))gives me the errorUncaught SyntaxError: Unexpected token ...