freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/nesting-for-loops.english.md

id, title, challengeType, videoUrl, forumTopicId

id	title	challengeType	videoUrl	forumTopicId
56533eb9ac21ba0edf2244e1	Nesting For Loops	1	https://scrimba.com/c/cRn6GHM	18248

Description

If you have a multi-dimensional array, you can use the same logic as the prior waypoint to loop through both the array and any sub-arrays. Here is an example:

var arr = [
  [1,2], [3,4], [5,6]
];
for (var i=0; i < arr.length; i++) {
  for (var j=0; j < arr[i].length; j++) {
    console.log(arr[i][j]);
  }
}

This outputs each sub-element in arr one at a time. Note that for the inner loop, we are checking the .length of arr[i], since arr[i] is itself an array.

Instructions

Modify function multiplyAll so that it multiplies the product variable by each number in the sub-arrays of arr

Tests

tests:
  - text: <code>multiplyAll([[1],[2],[3]])</code> should return <code>6</code>
    testString: assert(multiplyAll([[1],[2],[3]]) === 6);
  - text: <code>multiplyAll([[1,2],[3,4],[5,6,7]])</code> should return <code>5040</code>
    testString: assert(multiplyAll([[1,2],[3,4],[5,6,7]]) === 5040);
  - text: <code>multiplyAll([[5,1],[0.2, 4, 0.5],[3, 9]])</code> should return <code>54</code>
    testString: assert(multiplyAll([[5,1],[0.2, 4, 0.5],[3, 9]]) === 54);

Challenge Seed

function multiplyAll(arr) {
  var product = 1;
  // Only change code below this line

  // Only change code above this line
  return product;
}

multiplyAll([[1,2],[3,4],[5,6,7]]);

Solution

function multiplyAll(arr) {
  var product = 1;
  for (var i = 0; i < arr.length; i++) {
    for (var j = 0; j < arr[i].length; j++) {
      product *= arr[i][j];
    }
  }
  return product;
}

multiplyAll([[1,2],[3,4],[5,6,7]]);