Join three arrays to make one array which is a combination of a Cartesian product of rows with cols and dynamic relation with cells

Question

developers; I have three arrays: Days (columns), Subject (rows), Data(cells)

let Days = ["Monday", "Tuesday", "Wednesday"];
let Subject = [
  "Economics",
  "geography",
  "theatre",
  "music",
  "mathematics",
  "psychology",
  "marketing",
  "business",
  "journalism",
  "languages",
];
const Data = [
  ["10:00", "12:10", "13:30"],
  ["08:30", "12:10", "14:30"],
  ["14:10", "15:15", "19:10"],
  ["20:20", "20:50", "23:00"],
  ["09:10", "10:00", "19:00"],
  ["10:12", "16:40", "18:10"],
  ["08:30", "12:10", "14:30"],
  ["14:10", "15:15", "19:10"],
  ["20:20", "20:50", "23:00"],
  ["08:10", "14:20", "20:20"],
];

I wanna make a relation between those arrays:

I've tried something like playing with modulo and looping over product of rows and cells:

const cols = Days.length;
const rows = Subject.length;
const len = Subject.length * Days.length;
const table = [];
for (let i = 0, j = 0; i < len; i++) {
  table.push([
    Subject[i % rows],
    Days[j % cols],
    Data[i % rows][j % cols],
  ]);
  j++;
}
console.table(table);

But it gives results not expected in order:

I still trying to sorting it but does not work since sorting would sort in alphabet order which doesn't keep the order?

console.table(table.sort((a, b) => a[0].localeCompare(b[0])));

Thanks in advance, any suggestions are welcome and appreciated

why is `Data` grouped? what about this [question](https://stackoverflow.com/q/12303989/1447675)? — Nina Scholz, Dec 25 '21 at 12:05
You haven't made your expected output clear. Do you want to sort 'Subjects' together but in the original order of the 'Subject' array? If so just sort by `Subject.indexOf(a[0]) - Subject.indexOf(b[0])` instead of `localeCompare` — pilchard, Dec 25 '21 at 12:07

score 1 · Answer 1 · answered Dec 25 '21 at 12:11

you can do it easily by just lop twice, rows and cols.

let Days = ["Monday", "Tuesday", "Wednesday"];
let Subject = [
  "Economics",
  "geography",
  "theatre",
  "music",
  "mathematics",
  "psychology",
  "marketing",
  "business",
  "journalism",
  "languages",
];
const Data = [
  ["10:00", "12:10", "13:30"],
  ["08:30", "12:10", "14:30"],
  ["14:10", "15:15", "19:10"],
  ["20:20", "20:50", "23:00"],
  ["09:10", "10:00", "19:00"],
  ["10:12", "16:40", "18:10"],
  ["08:30", "12:10", "14:30"],
  ["14:10", "15:15", "19:10"],
  ["20:20", "20:50", "23:00"],
  ["08:10", "14:20", "20:20"],
];

const cols = Days.length;
const rows = Subject.length;
const len = Subject.length * Days.length;
const table = [];
for (let i = 0; i < rows; i++) {
  for (let j = 0; j < cols; j++) {
    table.push([
      Subject[i],
      Days[j],
      Data[i][j],
    ]);
  }
}
console.table(table);

Thanks, it seems simple with oneloop, I think I've just over-complicate it by using two loops! — XMehdi01, Dec 25 '21 at 12:22

score 1 · Accepted Answer · answered Dec 25 '21 at 12:50

Simply by doing the sort while doing the product process, as follows:

for (let i = 0; i < rows; i++) {
  for (let j = 0; j < cols; j++) {
      table.push([
      Subject[I],
      Days[j],
      Data[i][j],
      ]);
   }
 }

In this case, you will be iterating each row from Subject with all the corresponding values from Days, before moving to the next row of Subject, ending with the desired order of elements.

For example:
  the first iteration will be as follows (representing the first three row of the resulting array)
     i = 0  (Subject[i] = "Economics")
       j = 0  (Days[j] = "Monday") ---> Data[i][j] = "10:00"   
       j = 1  (Days[j] = "Tuesday") ---> Data[i][j] = "12:10"
       j = 2  (Days[j] = "Wednesday") ---> Data[i][j] = "13:30"

Join three arrays to make one array which is a combination of a Cartesian product of rows with cols and dynamic relation with cells

2 Answers2