Dart - find most common character in a string - dart

Question

I'm stuck on this common interview question using Dart. I need to return the most common character in a given string. I'm trying to create a map with a count for each character as the first step.
This is my progress so far:
main(List<String> arguments) {
maxChar('hello');
}
void maxChar(String word) {
Map<String, int> charMap = {};
int max = 0;
String maxChar = '';
word.split('').forEach((char) {
if(charMap.containsValue(char)) {
charMap[char]+1;
return;
} else {
charMap[char] = 1;
}
});
print(charMap);
}
Right now its not even counting the correct amount of the letter 'l'. It's outputting:
{h: 1, e: 1, l: 1, o: 1}
What am I doing wrong? Is there an easier way to return the most common character in a String in Dart?
Thanks!
EDIT:
Ok, I've solved it, but surely there is a more concise way of solving this problem. See my solution below:
main(List<String> arguments) {
print(max_char.maxChar('hello'));
}
String maxChar(String word) {
Map<String, int> charMap = {};
int max = -1;
String maxChar = '';
word.split('').forEach((char) {
if(charMap.containsKey(char)) {
charMap[char]++;
return;
} else {
charMap[char] = 1;
}
});
charMap.forEach((k,v) {
if(v > max) {
max = v;
maxChar = k;
}
});
return maxChar;
}

Answer 1

A shorter approach to counting the characters is definitely possible:
String charCount(String chars) {
int maxChar = -1;
int maxCount = 0;
var counts = <int, int>{};
for (var char in chars.runes) {
int count = counts.update(char, (n) => n + 1, ifAbsent: () => 1);
if (count > maxCount) {
maxCount = count;
maxChar = char;
}
}
return String.fromCharCode(maxChar);
}
If you just want to count the characters, you can remove all the lines mentioning maxCount and maxChar.
I use integers to represent the characters instead of strings. That's cheaper and just as precise, and it allows you to recognize and combine Unicode UTF-16 surrogates.