Data manipulation with a double data set

Question

Return an object where each key is an instructor name and each value is an array of the modules they can teach based on their skills.

Here are the datasets I am supposed to manipulate through:

const instructors = [
  { name: 'Pam', module: 2, teaches: ['scope', 'recursion', 'node'] },
  { name: 'Brittany', module: 2, teaches: ['oop', 'pwas'] },
  { name: 'Nathaniel', module: 2, teaches: ['oop', 'scope', 'mobile'] },
  { name: 'Robbie', module: 4, teaches: ['node', 'pwas'] },
  { name: 'Leta', module: 4, teaches: ['pwas', 'node', 'recursion'] },
  { name: 'Travis', module: 1, teaches: ['javascript', 'html', 'css'] },
  { name: 'Louisa', module: 1, teaches: ['javascript', 'html', 'css', 'node', 'pwas'] },
  { name: 'Christie', module: 3, teaches: ['javascript', 'react', 'node'] },
  { name: 'Will', module: 3, teaches: ['javascript', 'redux', 'react', 'oop', 'scope'] }
];

const cohorts = [
  { cohort: 1806, module: 1, studentCount: 30, curriculum: ['html', 'css', 'javascript'] },
  { cohort: 1804, module: 2, studentCount: 21, curriculum: ['javascript', 'css', 'recursion', 'scope', 'oop'] },
  { cohort: 1803, module: 3, studentCount: 20, curriculum: ['react', 'redux', 'html', 'javascript'] },
  { cohort: 1801, module: 4, studentCount: 18, curriculum: ['pwas', 'mobile', 'node', 'javascript', 'css'] }
];

Below is the code I have tried, I keep having issues iterating through two data sets, linking them together is tough!

This is what I've tried but cannot get the correct arrays to appear as values in the object:

let result1 = instructors.reduce((teacherObj, teacherName) => {
  if(!teacherObj[teacherName.name]) {
    teacherObj[teacherName.name] = []
    // console.log(instructors.map(a => a.module))
  }

  return teacherObj
}, {})
console.log(result1)

Expected Result:

{
   Pam: [2, 4],
   Brittany: [2, 4],
   Nathaniel: [2, 4],
   Robbie: [4],
   Leta: [2, 4],
   Travis: [1, 2, 3, 4],
   Louisa: [1, 2, 3, 4],
   Christie: [1, 2, 3, 4],
   Will: [1, 2, 3, 4]
}

Answer 1

First transform the cohorts array into an object indexed by curriculum, whose values are that curriculum's associated module(s), allowing for quick lookup. That is, an object like:

// modulesByCurriculum
{
  "html": [    // html is present in module 1 and 3
    1,
    3
  ],
  "css": [     // css is present in modules 1, 2, and 4
    1,
    2,
    4
  ], ...

This allows you to take a program name, like scope, and get its associated modules quickly.

Then, iterate through the instructors and look up each associated curriculum to find the modules, deduplicating via a Set:

const instructors = [
  { name: 'Pam', module: 2, teaches: ['scope', 'recursion', 'node'] },
  { name: 'Brittany', module: 2, teaches: ['oop', 'pwas'] },
  { name: 'Nathaniel', module: 2, teaches: ['oop', 'scope', 'mobile'] },
  { name: 'Robbie', module: 4, teaches: ['node', 'pwas'] },
  { name: 'Leta', module: 4, teaches: ['pwas', 'node', 'recursion'] },
  { name: 'Travis', module: 1, teaches: ['javascript', 'html', 'css'] },
  { name: 'Louisa', module: 1, teaches: ['javascript', 'html', 'css', 'node', 'pwas'] },
  { name: 'Christie', module: 3, teaches: ['javascript', 'react', 'node'] },
  { name: 'Will', module: 3, teaches: ['javascript', 'redux', 'react', 'oop', 'scope'] }
];

const cohorts = [
  { cohort: 1806, module: 1, studentCount: 30, curriculum: ['html', 'css', 'javascript'] },
  { cohort: 1804, module: 2, studentCount: 21, curriculum: ['javascript', 'css', 'recursion', 'scope', 'oop'] },
  { cohort: 1803, module: 3, studentCount: 20, curriculum: ['react', 'redux', 'html', 'javascript'] },
  { cohort: 1801, module: 4, studentCount: 18, curriculum: ['pwas', 'mobile', 'node', 'javascript', 'css'] }
];

const modulesByCurriculum = cohorts.reduce((a, { module, curriculum }) => {
  curriculum.forEach((currName) => {
    if (!a[currName]) {
      a[currName] = [];
    }
    a[currName].push(module);
  });
  return a;
}, {});
const output = instructors.reduce((a, { name, teaches }) => {
  a[name] = [...new Set(
    teaches.flatMap(currName => modulesByCurriculum[currName])
  )];
  return a;
}, {});
console.log(output);

If you can't use flatMap, you can spread into concat instead:

const instructors = [
  { name: 'Pam', module: 2, teaches: ['scope', 'recursion', 'node'] },
  { name: 'Brittany', module: 2, teaches: ['oop', 'pwas'] },
  { name: 'Nathaniel', module: 2, teaches: ['oop', 'scope', 'mobile'] },
  { name: 'Robbie', module: 4, teaches: ['node', 'pwas'] },
  { name: 'Leta', module: 4, teaches: ['pwas', 'node', 'recursion'] },
  { name: 'Travis', module: 1, teaches: ['javascript', 'html', 'css'] },
  { name: 'Louisa', module: 1, teaches: ['javascript', 'html', 'css', 'node', 'pwas'] },
  { name: 'Christie', module: 3, teaches: ['javascript', 'react', 'node'] },
  { name: 'Will', module: 3, teaches: ['javascript', 'redux', 'react', 'oop', 'scope'] }
];

const cohorts = [
  { cohort: 1806, module: 1, studentCount: 30, curriculum: ['html', 'css', 'javascript'] },
  { cohort: 1804, module: 2, studentCount: 21, curriculum: ['javascript', 'css', 'recursion', 'scope', 'oop'] },
  { cohort: 1803, module: 3, studentCount: 20, curriculum: ['react', 'redux', 'html', 'javascript'] },
  { cohort: 1801, module: 4, studentCount: 18, curriculum: ['pwas', 'mobile', 'node', 'javascript', 'css'] }
];

const modulesByCurriculum = cohorts.reduce((a, { module, curriculum }) => {
  curriculum.forEach((currName) => {
    if (!a[currName]) {
      a[currName] = [];
    }
    a[currName].push(module);
  });
  return a;
}, {});
const output = instructors.reduce((a, { name, teaches }) => {
  a[name] = [...new Set(
    [].concat(...teaches.map(currName => modulesByCurriculum[currName]))
  )];
  return a;
}, {});
console.log(output);