js统计字符串中每个字符出现的频率

// 统计字符出现率
function fn(str=""){
        let frequency = {}
        for (let letter of str) {
            if (frequency[letter]) {
                frequency[letter]++;
            } else {
                frequency[letter] = 1;
            }
        }
        console.log(frequency)
    }

fn("skjlaldkfasjhdiuyqwuhekj12938934732")