Algorithms in Javascript: CTCI 1.8 Zero Matrix: Write an algorithm such that if an element in an MxN matrix is 0, its entire row and column are set to 0.

ctci-1.8-zero-matrix.js

const zeroMatrix = (m) => {
    const sizeY = m.length, 
        sizeX = m[0].length;
    let charMap = new Map();
    
    for(let r=0; r<sizeY; r++){
      for(let c=0; c<sizeX; c++){
        if(m[r][c] === 0) {
          charMap.set(r, c);
        }
      }
    }
    
    for (let [key, value] of charMap.entries()) {
      for(let r=0; r<sizeX; r++){
        m[r][value] = 0;
      }
      for(let c=0; c<sizeY; c++){
        m[key][c] = 0;
      }
    }
    
    return m;
}

var a = [[1,2,0],
         [4,5,6],
         [0,8,9]];
var za = zeroMatrix(a);
console.log(za);