How to concatenate strings in an array of array with Ramda.js

Question

Given a 2d matrix of strings, I would like to concatenate the elements in the sublists based on their position.

e.g. Given this data structure as input:

[['x','y' ,'z'],['A', 'B', 'C'], ['a', 'b', 'c']]

The algorithm would produce the output:

['xAa', 'yBb', 'zCc']

I tried R.transpose, but it gets me [['x','A','a'], ['y', 'B', 'b'], ['z', 'C', 'c']], however I couldn't find a way to concatenate the nested strings.

I also tried R.zipWith, but it doesn't look ideal since R.zipWith takes only two arguments so that I need to apply it twice to get the output.

Chad S. · Accepted Answer · 2020-08-28 21:32:06Z

2

You weren't that far off I think.

With transpose you managed to get this:

[['x','A','a'], ['y', 'B', 'b'], ['z', 'C', 'c']]

Then you just need to map over this array of arrays and join each of them.

e.g.

const {compose, map, join, transpose } = R
const concat_arr = compose(map(join("")), transpose);
const result = concat_arr([['x','y' ,'z'],['A', 'B', 'C'], ['a', 'b', 'c']]);
console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.1/ramda.min.js"></script>

Where compose, map, join and transpose are all Ramda functions.

The initial input goes to transpose
The result of transpose(arr) is given to map(join("")) which applies join("") to all sub arrays

edited Aug 28, 2020 at 21:32

Chad S.

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answered Aug 28, 2020 at 12:26

customcommander

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