continually add values in javascript with while loop

Question

I'm a newbie to Javascript so please bear with me for this basic question,

I'm trying to get my function to add all the individual digits in a string together, and then keep doing this until I'm left with a single digit!

3253611569939992595156

113 // result of the above digits all added together

5 //result of 1+1+3

I've created a while loop, but it only adds the numbers together once, it dosn't repeat until a single digit and I can't work out why!

function rootFunc(n) {
  var splite = n.toString().split('').map(x => Number(x)); //converts the number to a string, splits it and then converts the values back to a number

  while (splite.length > 1) {
    splite = splite.reduce(getSum);
  }

  return splite;
}

console.log(rootFunc(325361156993999259515));

function getSum(total, num) {
  return total + num;
}

At a first glance I'm going to say that after you call your reduce fn and modify splite, it becomes a single value, so you won't be looping again. I recommend going over the docs for reduce — Felipe
– Felipe, Commented May 10, 2018 at 16:43

tadman · Accepted Answer · 2018-05-10 16:43:39Z

2

You're reducing properly, but what you're not doing is re-splitting. Try breaking this out into separate functions:

function digits(n) {
  return n.toString().split('').map(x =>Number(x));
}

Then split each time:

function rootFunc(n) {
  var d = digits(n);
  while (d.length > 1) {
    d = digits(d.reduce(getSum));
  }

  return d;
}

answered May 10, 2018 at 16:43

tadman

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Comments

Scott Picquerey · Accepted Answer · 2018-05-10 16:46:38Z

1

The problem here is that you return the result after the first splice. You need to have a recursive function. To do this, you can put this before the return :

  if(splite > 9) splite = rootFunc(splite);

This way, you check if the result is greater than 10, if not you do the function with the remaining digits

answered May 10, 2018 at 16:46

Scott Picquerey

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Comments

Bezlonir · Accepted Answer · 2018-05-10 18:56:30Z

1

I was looking this over in jsfiddle, and your number isn't being passed to exact precision, so just console logging n as soon as you call rootFunc, you've already lost data. Otherwise, to fix your loop, you need to remap splite to a string before the end of your codeblock since your while statement is checking .length, which needs to be called on a string. Put this piece of code at the end of the block: splite = splite.toString().split('').map(x =>Number(x));

edited May 10, 2018 at 18:56

answered May 10, 2018 at 17:10

Bezlonir

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1 Comment

Lance McCarthy Over a year ago

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