Javascript:Nesting for Loops

Curriculum Help
1 
function multiplyAll(arr) {
  var product = 1;
  // Only change code below this line
  for(var i=0;i<arr.length;i++){
    for(var q=0;q<arr[i].length;q++){
      product*=arr[i][q];
    }
  }
  // Only change code above this line
  return product;
}

// Modify values below to test your code
multiplyAll([[1,2],[3,4],[5,6,7]]);

I got this one and it is working.But i don’t know how it is working.Anyone please explain it!

2

I think you are having trouble with product*=arr[i][q]
see this image. this might help if not let me know.

here I0 I1 I2 is for 1st loop and q0 q1 q2 q3 q4 q5 for 2nd loop.

2darray
2darray1152×648 5.69 KB

3

could you please explain this image.i didn’t get it!

4

start with an array of 3 arrays
first for loop:
i = 0, arr length = 3
…second for loop:
…q = 0, arr [position 0] length = 2
…multiply product by element at
… …arr [position 0] element[ 0 ] , then …arr [position 0] element[1]
so, position[0] is the variable … i
and element[0] is the variable …q
since the first array element has 2 items,[1,2]… q starts at 0, goes to 1, then
stops because incrementing q to 2 … no longer is < the element length.
so i goes from 0 to 1, and you start all over with the new array at the next position.
i = 1 …the array at arr[1] is … [3,4] …and q is set back to 0 to check the first element?

did I just make it worse? lol

5

see
for loop 1------ i=0
-----for loop 2------- q=0;
--------product = 1* arr[i,q] i.e [0,0] i.e 1(see the img for position) so position = 11 i.e 1;
-----for loop 2--------- q=1;
------- product = 1 arr[i,q]i.e [0,1] i.e 2(see the img for position) so position = 12 i.e 2;
for loop 1---------- i=1
-----for loop 2---------q=0;(sorry,that q2 in image is actually q0 nd q3 is q1);
--------product = 2arr[i,q] i.e [1,0] i.e 3 so position = 2*3 i.e 6;
and this will go like this until the condition bacome false.