freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/rosetta-code/element-wise-operations.english.md

title, id, challengeType

title	id	challengeType
Element-wise operations	599c333915e0ea32d04d4bec	5

Description

Implement basic element-wise matrix-matrix and scalar-matrix operations.

Implement:

::* addition

::* subtraction

::* multiplication

::* division

::* exponentiation

The first parameter will be the operation to be performed, for example : "m_add" for matrix addition and "s_add" for scalar addition. The second and third parameters will be the matrices on which the operations are to be performed.

Instructions

Tests

tests:
  - text: <code>operation</code> is a function.
    testString: 'assert(typeof operation === "function", "<code>operation</code> is a function.");'
  - text: '<code>operation("m_add",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[2,4],[6,8]]</code>.'
    testString: 'assert.deepEqual(operation("m_add", [[1, 2], [3, 4]], [[1, 2], [3, 4]]), [[2, 4], [6, 8]], "<code>operation("m_add",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[2,4],[6,8]]</code>.");'
  - text: '<code>operation("s_add",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[3,4],[5,6]]</code>.'
    testString: 'assert.deepEqual(operation("s_add", [[1, 2], [3, 4]], 2), [[3, 4], [5, 6]], "<code>operation("s_add",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[3,4],[5,6]]</code>.");'
  - text: '<code>operation("m_sub",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[0,0],[0,0]]</code>.'
    testString: 'assert.deepEqual(operation("m_sub", [[1, 2], [3, 4]], [[1, 2], [3, 4]]), [[0, 0], [0, 0]], "<code>operation("m_sub",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[0,0],[0,0]]</code>.");'
  - text: '<code>operation("m_mult",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,4],[9,16]]</code>.'
    testString: 'assert.deepEqual(operation("m_mult", [[1, 2], [3, 4]], [[1, 2], [3, 4]]), [[1, 4], [9, 16]], "<code>operation("m_mult",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,4],[9,16]]</code>.");'
  - text: '<code>operation("m_div",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,1],[1,1]]</code>.'
    testString: 'assert.deepEqual(operation("m_div", [[1, 2], [3, 4]], [[1, 2], [3, 4]]), [[1, 1], [1, 1]], "<code>operation("m_div",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,1],[1,1]]</code>.");'
  - text: '<code>operation("m_exp",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,4],[27,256]]</code>.'
    testString: 'assert.deepEqual(operation("m_exp", [[1, 2], [3, 4]], [[1, 2], [3, 4]]), [[1, 4], [27, 256]], "<code>operation("m_exp",[[1,2],[3,4]],[[1,2],[3,4]])</code> should return <code>[[1,4],[27,256]]</code>.");'
  - text: '<code>operation("m_add",[[1,2,3,4],[5,6,7,8]],[[9,10,11,12],[13,14,15,16]])</code> should return <code>[[10,12,14,16],[18,20,22,24]]</code>.'
    testString: 'assert.deepEqual(operation("m_add", [[1, 2, 3, 4], [5, 6, 7, 8]], [[9, 10, 11, 12], [13, 14, 15, 16]]), [[10, 12, 14, 16], [18, 20, 22, 24]], "<code>operation("m_add",[[1,2,3,4],[5,6,7,8]],[[9,10,11,12],[13,14,15,16]])</code> should return <code>[[10,12,14,16],[18,20,22,24]]</code>.");'

Challenge Seed

function operation (op, arr1, arr2) {
  // Good luck!
}

Solution

function operation(op, arr1, arr2) {
  const ops = {
    add: ((a, b) => a + b),
    sub: ((a, b) => a - b),
    mult: ((a, b) => a * b),
    div: ((a, b) => a / b),
    exp: ((a, b) => Math.pow(a, b))
  };
  const ifm = op.startsWith('m');
  const doOp = ops[op.substring(2)];
  for (let i = 0; i < arr1.length; i++) {
    for (let j = 0; j < arr1[0].length; j++) {
      arr1[i][j] = doOp(arr1[i][j], (ifm) ? (arr2[i][j]) : (arr2));
    }
  }
  return arr1;
}