判断一个字符串出现的次数？

  const str = 'asddfgdfwwqeweqwezczxcsdfgdgd';

    function getStrCount(str, word) {
        let arr = Array.from(str);
        let map = new Map();

        for (let i = 0; i < arr.length; i++) {
            if (map.has(arr[i])) {
                //  console.log(map.get(arr[i]));
                let sum = map.get(arr[i]);
                map.set(arr[i], ++sum);

            } else {
                map.set(arr[i], 1);
            }
        }
        return map.get(word);
    };
    console.log(getStrCount(str, 'd'));