How can I break numbers into their digit values?

Question

As part of a Roman numerals converter algorithm, I would like to break a given number into their digit values. What I precisely want to do is as follows:

1984 = 1000+900+80+4

It would be better to let you know where I will use the outcome. I will push the result in an array and match with their Roman numeral counterpart, e.g. 1000 = M, 900 = CM, 80 = LXXX, 4 = IV.

1984 = MCMLXXXIV

What kind of function is needed to produce the expected output?

apparently you can use this https://blog.usejournal.com/create-a-roman-numerals-converter-in-javascript-a82fda6b7a60 — jaswanth, Apr 20 '20 at 15:05
My methodology differs from most of the others on the web, but this could also be a great use. — Mehmet Eyüpoğlu, Apr 20 '20 at 15:09
ok got it for the first part you can try this `a=1984;a1=String(a).split("").map((x, i)=>{return parseInt(x+"0".repeat(jash.length-i-1))})` — jaswanth, Apr 20 '20 at 15:19
https://stackoverflow.com/questions/9083037/convert-a-number-into-a-roman-numeral-in-javascript — epascarello, Apr 20 '20 at 15:40
Does this answer your question? [Convert a number into a Roman Numeral in javaScript](https://stackoverflow.com/questions/9083037/convert-a-number-into-a-roman-numeral-in-javascript) — Brian Tompsett - 汤莱恩, Apr 25 '20 at 08:13

alexortizl · Answer 1 · 2020-04-20T15:35:51.200

1

Here are two small algorithms to do just that:

function separate(number) {
  const length = number.toString().length;
  const result = [0];
  let step = 1;

  for (let i= 0; i< length; i++) {
    step *= 10;
    let part = number % step;

    result.forEach(previous => {
      part -= previous;
     });

    result[i] = part;
  }

  return result;
}

and

function separate(number) {
  const str = number.toString();
  const result = [];

  for (var i = 0; i < str.length; i++) {
    result[i] = str.charAt(i) * Math.pow(10, i);
  }

  return result;  
}

It returns an array with each separated number

edited Apr 20 '20 at 15:35

answered Apr 20 '20 at 15:21

alexortizl

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step *= 10; produces error due to its being a constant. – Mehmet Eyüpoğlu Apr 20 '20 at 15:31
@MehmetEyüpoğlu you're right sorry I had these algorithms in C and I missed that when I transpiled them to JavaScript. Should be fixed now – alexortizl Apr 20 '20 at 15:37

score 1 · Accepted Answer · answered Apr 20 '20 at 15:38

1

I tweaked it into this one-liner:

Array.from((1984).toString()).reverse().map((d, i) => d * 10 ** i)

This will give you the parts in reverse (least significant digit first); depending on your need you may want to add another .reverse() at the end.

answered Apr 20 '20 at 15:38

Touffy

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let separator = (num) => { let array = Array .from((num).toString()) .reverse() .map((d, i) => d * 10 ** i) .sort((a,b) => b - a ) return array; } – Mehmet Eyüpoğlu Apr 20 '20 at 15:53
1

the `sort()` is overkill, you should just use `reverse()` : `let separator = num => Array.from(num.toString()).reverse().map((d, i) => d * 10 ** i).reverse()` – Touffy Apr 20 '20 at 15:58

How can I break numbers into their digit values?

2 Answers2