Array of numbers to Array of one string

I need to [1, 2, 3] over to [‘123’].
I must return [1, 2, 3] over to [‘123’] while using an arrow function (no regex):

Must be used:

---

const functionOne = (arrayOne) => {

};

console.log(functionOne([1, 2, 3]));

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So, I tried the following:

First, I created a string. This gave me 1,2,3

Then, I removed the commas, so, I could join the numbers. This gave me 123.

Finally, I tried to put back the number as a string into the array but this didn’t work. This gave me ['1', '2', '3'] instead of ['123']. I think the .split method is what is wrong in my code but I cannot find another one (currently learning JavaScript).

const functionOne = (arrayOne) => {

  let stepOne = arrayOne.toString(arrayOne => arrayOne.toString());

  console.log(stepOne);

  stepOne = stepOne.split(',').join('');

  console.log(stepOne);

  return stepOne.split('');

};

console.log(functionOne([1, 2, 3]));