Matrix Multiplication in Typescript

Question

I would like some help on making my solution more functional. At present, I rely heavily on using indexes in my map functions. I am also seeking general feedback and advice, thanks.

export const getMatrixColumns = (a: number[][]) => {
 return a[0].length;
};
export const getMatrixRows = (a: number[][]) => {
 return a.length;
};
export const matricesAreValid = (a: number[][], b: number[][]) => {
 return getMatrixColumns(a) === getMatrixRows(b);
};
export const generateEmptyMatrix = (rows: number, cols: number) => {
 return [...Array(rows)].fill(0).map(() => [...Array(cols)].fill(0));
};
export const dotProduct = (a: number[], b: number[]) => {
 return a.map((value, i) => value * b[i]).reduce((acc, val) => acc + val, 0);
};
export const multiplyMatrices = (a: number[][], b: number[][]) => {
 if (matricesAreValid(a, b)) {
 const rows = getMatrixRows(a);
 const cols = getMatrixColumns(b);
 return generateEmptyMatrix(rows, cols).map((resultRow, i) =>
 resultRow.map((element: number, j: number) => {
 const column = b.map(row => row[j]);
 const row = a[i];
 return dotProduct(row, column);
 })
 );
 }
};

Answer 1

Concise Function Body

The function body of an arrow function can be concise.

For instance can getMatrixColumns shorten to

export const getMatrixColumns = (a: number[][]) => a[0].length;

---

Method Name

The method names getMatrixColumns and getMatrixRows let me expect that the the methods return a number[] instead of a number.

A better fit are getMatrixColumnLength and getMatrixRowLength.

---

Redundant Method Names

Each method name expect dotProduct contains some how the word matrix.

It is sufficient if the methods are grouped in a Matrix module and have names like:

// in matrix.js
export const columnLenghtOf = (a: number[][]) => 
 a[0].length;
export const rowLengthOf = (a: number[][]) => 
 a.length;
export const areValid = (a: number[][], b: number[][]) =>
 columnLenghtOf(a) === columnLenghtOf(b);
/* ... */

---

Type Alias

Matrix could be a type alias for number[][]:

// in matrix.js
type Matrix = number[][]
export const columnLenghtOf = (a: Matrix) => 
 a[0].length;
```