How do I sort an array of strings numerically with Ramda?

Question

I'm trying to sort the following object's keys properly:

const data = {
  '0 - 4': [...],
  '5 - 9': [...],
  '10 - 14': [...],
  '15 - 19': [...],
};

By doing:

const sort = R.sortBy(R.toLower);
return R.compose(sort, R.keys)(data);

But it always ends up coming out as:

['0 - 4', '10 - 14', '15 - 19', '5 - 9'];

Because it's treating the numbers as a string and a string that starts with 5 is supposedly higher than a string that starts with a 1. Would anyone know how to use Ramda to properly sort this so that it comes out as

['0 - 4', '5 - 9', '10 - 14', '15 - 19'];

Answer 1

You can use String.localCompare() with the numeric: true option in the comparator function:

 const data = { '0 - 4': [], '5 - 9': [], '10 - 14': [], '15 - 19': [], }; const sort = R.sort((a, b) => a.localeCompare(b, undefined, { numeric: true })); const result = R.compose(sort, R.keys)(data); console.log(result);

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And this is how you would do that without Ramda:

 const data = { '0 - 4': [], '5 - 9': [], '10 - 14': [], '15 - 19': [], }; const fn = obj => Object.keys(obj).sort((a, b) => a.localeCompare(b, undefined, { numeric: true })); const result = fn(data); console.log(result);

Answer 2

Use parseInt instead of R.toLower :

const sort = R.sortBy(parseInt);

R.toLower doesn't make sense because it won't affect the strings anyway because they only contain numbers, dashes and spaces, and the result of calling toLower will still be a string, the same string.

parseInt , on the other hand, will return the left-side number of each string (for example parseInt('10 - 14') is the number 10 , not a string), which will then be used by sortBy to sort the strings.

Demo:

 const data = { "10 - 14'": [], "5 - 9": [], "15 - 19": [], "0 - 4": [] }; const sort = R.sortBy(parseInt); const result = R.compose(sort, R.keys)(data); console.log(result);

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