Examples:
maxChar("abcccccccd") === "c"
maxChar("apple 1231111") === "1"
function maxChar(str) { const charMap = {}; let max = 0; let maxCh = ''; for (let ch of str) { if (charMap[ch]) { charMap[ch]++; } else { charMap[ch] = 1; } } for (let ch in charMap) { if (charMap[ch] > max) { max = charMap[ch]; maxCh = ch; } } return maxCh; }