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ach5910's solution

to Transpose in the JavaScript Track

Published at May 05 2021 · 0 comments
Test suite

Given an input text output it transposed.

Roughly explained, the transpose of a matrix:


is given by:


Rows become columns and columns become rows. See https://en.wikipedia.org/wiki/Transpose.

If the input has rows of different lengths, this is to be solved as follows:

  • Pad to the left with spaces.
  • Don't pad to the right.

Therefore, transposing this matrix:


results in:


And transposing:


results in:


In general, all characters from the input should also be present in the transposed output. That means that if a column in the input text contains only spaces on its bottom-most row(s), the corresponding output row should contain the spaces in its right-most column(s).


Go through the setup instructions for Javascript to install the necessary dependencies:



Please cd into exercise directory before running all below commands.

Install assignment dependencies:

$ npm install

Making the test suite pass

Execute the tests with:

$ npm test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing xtest to test.

Submitting Solutions

Once you have a solution ready, you can submit it using:

exercism submit transpose.js

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

Exercise Source Credits

Reddit r/dailyprogrammer challenge #270 [Easy]. https://www.reddit.com/r/dailyprogrammer/comments/4msu2x/challenge_270_easy_transpose_the_input_text


import { transpose } from './transpose';

describe('Transpose', () => {
  test('empty string', () => {

  xtest('two characters in a row', () => {
    const input = ['A1'];
    const expected = ['A', '1'];

  xtest('two characters in a column', () => {
    const input = ['A', '1'];
    const expected = ['A1'];

  xtest('simple', () => {
    const input = ['ABC', '123'];
    const expected = ['A1', 'B2', 'C3'];

  xtest('single line', () => {
    const input = ['Single line.'];
    const expected = [
      ' ',

  xtest('first line longer than second line', () => {
    const input = ['The fourth line.', 'The fifth line.'];
    const expected = [
      '  ',
      'h ',
      ' l',

  xtest('second line longer than first line', () => {
    const input = ['The first line.', 'The second line.'];
    const expected = [
      '  ',
      ' d',
      'l ',
      ' .',

  xtest('square', () => {
    const input = ['HEART', 'EMBER', 'ABUSE', 'RESIN', 'TREND'];
    const expected = ['HEART', 'EMBER', 'ABUSE', 'RESIN', 'TREND'];

  xtest('rectangle', () => {
    const input = ['FRACTURE', 'OUTLINED', 'BLOOMING', 'SEPTETTE'];
    const expected = [

  xtest('triangle', () => {
    const input = ['T', 'EE', 'AAA', 'SSSS', 'EEEEE', 'RRRRRR'];
    const expected = [
      ' EASER',
      '  ASER',
      '   SER',
      '    ER',
      '     R',

  xtest('many lines', () => {
    const input = [
      'Chor. Two households, both alike in dignity,',
      'In fair Verona, where we lay our scene,',
      'From ancient grudge break to new mutiny,',
      'Where civil blood makes civil hands unclean.',
      'From forth the fatal loins of these two foes',
      "A pair of star-cross'd lovers take their life;",
      "Whose misadventur'd piteous overthrows",
      "Doth with their death bury their parents' strife.",
      "The fearful passage of their death-mark'd love,",
      "And the continuance of their parents' rage,",
      "Which, but their children's end, naught could remove,",
      "Is now the two hours' traffic of our stage;",
      'The which if you with patient ears attend,',
      'What here shall miss, our toil shall strive to mend.',
    const expected = [
      'hnrhr hohnhshh',
      'o oeopotedi ea',
      'rfmrmash  cn t',
      '.a e ie fthow ',
      ' ia fr weh,whh',
      'Trnco miae  ie',
      'w ciroitr btcr',
      ' eeih a uote  ',
      'hrnl sdtln  is',
      'oot ttvh tttfh',
      'un bhaeepihw a',
      'e,ro -trsui ol',
      'h uofcu sarhu ',
      'owddarrdan o m',
      "lhg to'egccuwi",
      'sr als t  ists',
      ",ebk 'phool'h,",
      '  reldi ffd   ',
      'bweso tb  rtpo',
      'oea ileutterau',
      't kcnoorhhnatr',
      "hl isvuyee'fi ",
      ' atv es iisfet',
      'ayoior trr ino',
      'l  lfsoh  ecti',
      'ion   vedpn  l',
      'kuehtteieadoe ',
      '   nekt te  rh',
      'ncuse ra-tau l',
      ' et  tormsural',
      "dniuthwea'g t ",
      'iennwesnr hsts',
      'g,ycoi tkrttet',
      "n ,l r s'a anr",
      "i  ef  'dgcgdi",
      't  aol   eoe,v',
      'y  nei sl,u; e',
      ',  .sf to l   ',
      '     e rv d  t',
      '     ; ie    o',
      '       f, r   ',
      '       e  e  m',
      '       .  m  e',
      '          o  n',
      '          v  d',
      '          e  .',
      '          ,',
// This is only a SKELETON file for the 'Transpose' exercise. It's been provided as a
// convenience to get you started writing code faster.

export const transpose = (arr) => {
    const maxLen = arr.reduce((acc, str) => Math.max(acc, str.length), 0);
    const arr2 = [];
    for (let j = 0; j < maxLen; j++){
        let str = '';
        for (let i = 0; i < arr.length; i++){
            str = `${str}${arr[i][j] ?? ' '}`
        arr2[j] = str;
    if (maxLen > 0){
        arr2[maxLen - 1] = arr2[maxLen - 1].trimEnd();
    return arr2;

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