when you return you don't need to add the break couse you already breaking the code

I see... I have to go back to studying.

yeah, looks like he's just too lazy to make a new variable

I just tested it again in codewars with 10,000,000,000 and it still works fine. I also tried with other several higher numbers and it always works fine and returns the expected value:

• 92,000,000,123 and returned 8 (true)
• 999,999,999,999 and returned 9 (true)
• 9,111,999,999,999 and returned 3 (true)
• 88,888,888,888,888 and returned 4 (true)
• 123,123,123,123,123 and returned 3 (true)
• 123,456,789,012,345 and returned 6 (true)

Here you can try the tests:

const chai = require("chai");
const assert = chai.assert;
chai.config.truncateThreshold=0;

describe("Tests", () => {
  it("test", () => {
    assert.strictEqual( digitalRoot(10000000001), 2)
    assert.strictEqual( digitalRoot(92000000123), 8)
    assert.strictEqual( digitalRoot(999999999999), 9)
    assert.strictEqual( digitalRoot(9111999999999), 3)
    assert.strictEqual( digitalRoot(88888888888888), 4)
    assert.strictEqual( digitalRoot(123123123123123), 3)
    assert.strictEqual( digitalRoot(123456789012345), 6)
  });
});

This dude must be a scientist in NASA

interesting

he doesn't use template literals.

This comment has been deleted.

Why do you have a zero at the end of the callback function?

Интересная техника кода

It works well, but it must be refactored as it's really difficult to follow the logic let alone maintain this solution.

I really liked your use of reduce. I'm happy I looked it up. Such a handy little function

Best sol of this kata