add items to a generator while looping through each unique element of it

appendableSetGenerator.ts

function appendableSetGenerator<T>(initialToTry?: IterableIterator<T>, tried = new Set<T>()): [Generator<T>, (...values: T[]) => void] {
    const toTry = new Set<T>(initialToTry || null)
    return [
        (function* () {
            while (toTry.size) {
                for (const value of toTry.values()) {
                    tried.add(value)
                    toTry.delete(value)
                    yield value
                    break
                }
            }
        })(),
        (...values) => {
            for (const value of values) {
                if (!tried.has(value)) {
                    toTry.add(value)
                }
            }
        },
    ]
}

example.ts

const [elems, addToElems] = appendableSetGenerator<number>()

for (const elem in elems) {
    // do something
    addToElems(...)
}