returns array of a matrix collumn's max lengths

colMax.js

function colMax(mrx) {
  let mLen = [];
  let len = 0, lVal = true;
  for(var m=0; m<mrx[0].length; m++) {
    for(var n in mrx) {
      let eLen = mrx[n][m].toString().length;
      lVal = eLen ? lVal<eLen : lVal;
      if(len<eLen)
        len = eLen;
    }
    mLen.push(len);
    len -= len;
    lVal = true;
  }
  return mLen;
}

// push lVal in <line 11> instead to get booleans of wheather the length in- or decreased