https://www.youtube.com/watch?v=5dJSZLmDsxk&t=11s

negative-number-matrix.js

/*
* Count Negative Integers in Matrix
*/

M = [                                                                                                                                              
  [ -1, 3,  4, 1],                                                                                                                               
  [  2, 2,  4, 9],                                                                                                                               
  [  4, 5, -7, 9]                                                                                                                                
 ]                                                                                                                                               

function findNegative(M, n, m) {                                                                                                                   
 count = 0                                                                                                                                         
 i = 0                                                                                                                                             
 j = m - 1                                                                                                                                         

 while (j >= 0 && i < n) {                                                                                                                         
  if(M[i][j] < 0){                                                                                                                                 
  count += (j + 1)                                                                                                                                
  i += 1                                                                                                                                          
 } else {                                                                                                                                         
  j -= 1                                                                                                                                          
 }                                                                                                                                                
}                                                                                                                                                 
 console.log(count)                                                                                                                                
}                                                                                                                                                  

findNegative(M, 3, 4) 

Yay https://gist.github.com/lubien/662c9e2e474b123f77420dde3a38a35b
ＣＯＭＰＯＳＥ　ＥＶＥＲＹＴＨＩＮＧ

https://gist.github.com/Woodsphreaker/cb5d675744b0b0b11aaba111200d586e

Using map and filter

function count_negative(M) {
  var n_count = 0;
  M.map(
    function (row) {
      n_count += row.filter(
        function (item) {
          return item < 0;
        }
      ).length;
    }
  );
  return n_count;
}

const countNegatives = mtx => mtx.reduce((acc, x) => acc.concat(x)).filter(x => x < 0).length;