In Node/Javascript, how do I map cardinality from string to int?

Question

For example, I have user input any string: "1st", "2nd", "third", "fourth", "fifth", "9999th", etc. These are just examples, the user can input any string.

I want to map this to integer cardinality:

"1st" -> 0
"2nd" -> 1
"third" -> 2
"fourth" -> 3
"fifth" -> 4
"9999th" -> 9998

So I need some kind of function where:

   function mapCardinality(input: string): number{
     let numberResult:number = ??
     return numberREesult;
   }

and I can call it like this:

console.log(
  mapCardinality("1st"), // print 0
  mapCardinality("2nd"), // print 1
  mapCardinality("third"), // print 2
  mapCardinality("fourth"), // print 3
  mapCardinality("fifth"), // print 4
  mapCardinality("9999th") // print 9998
);

How do you get that _string as input_? For converting it into corresponding integers you can use an object: `{ "1st": 0, "2nd": 1, ... }` — Ram, Oct 04 '18 at 19:51
I can't JUST map them, the examples are just examples, what if the user input 99th? I can't just sit there and map every integer in the universe. — Bill Software Engineer, Oct 04 '18 at 19:55
Why is it 1st, 2nd, third .. why not 1st, 2nd, 3rd or first, second, third .. shouldn't you just stick with one? — rmn, Oct 04 '18 at 20:05
Related: [How to read values from numbers written as words?](https://stackoverflow.com/questions/70161/how-to-read-values-from-numbers-written-as-words) — CRice, Oct 04 '18 at 20:10

Jonas Wilms · Answer 1 · 2018-10-04T20:04:27.447

0

Just look it up in an array or parse it as number:

const mapCardinality = c => {
   const pos = ["1st", "2nd", "third", "fourth",  "fifth"].indexOf(c);
   return pos === -1 ? parseInt(c, 10) - 1 : pos;
};

edited Oct 04 '18 at 20:04

answered Oct 04 '18 at 19:56

Jonas Wilms

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That definitely wold not work, as these are just example, what if the user wrote 999th? I can't write a map for every cardinality in the universe. – Bill Software Engineer Oct 04 '18 at 19:56
1

@bill and what if he wrote "ninehundredninetynineth" ? – Jonas Wilms Oct 04 '18 at 19:58
I am just going to tell the user that I didn't understand that one – Bill Software Engineer Oct 04 '18 at 20:00
@bill then why couldn't you just tell the user to input the `_ _ _ th` with numbers? That would make everyones lifes easier – Jonas Wilms Oct 04 '18 at 20:02
i was hoping there is already a library in npm that I could use. I would do regex if no existing solution exist. – Bill Software Engineer Oct 04 '18 at 20:03
1

@Bill note that asking for library recommendations is off-topic for SO: https://meta.stackoverflow.com/questions/254393/what-exactly-is-a-recommendation-question – Hamms Oct 04 '18 at 20:19

score 0 · Answer 2 · answered Oct 04 '18 at 20:23

I'd first ask what are the suffixes for all of the inputs?

'nd', 'rd', 'st', 'th' (most numbers)

If they enter an integer with the above prefixes then you could write the following function:

const getInteger = input => input.slice(0, -2);
const num = getInteger('999th');
console.log(num); // prints "999"

If they enter the elongated variant, it becomes much more complex, especially when it comes to typos, lack of spaces, etc. One way could be to map single digit words ('one', 'two', etc), tens ('ten', 'twenty', etc'), hundreds, thousands, and so on instead of every number imaginable. I would then parse and find matching words to give a result. That being said it is still limiting. I would strongly suggest limiting user input formats. Why can't the user input an integer?

const cardinalDictionary = {
  'zero': 0,
  'one': 1,
  ...,
  'twenty',
  ...,
  'hundred': 100,
  'thousand': 1000,
};

In Node/Javascript, how do I map cardinality from string to int?

2 Answers2