使用正则匹配

let str = readline()
let letter = 0, blank =0, number = 0, other = 0;
for(let i = 0; i< str.length; i ++){
    if(/^[a-zA-Z]$/.test(str[i])){
        letter++
        continue
    }
    if(/^[ ]$/.test(str[i])){
        blank++
        continue
    }
    if(/^[0-9]$/.test(str[i])){
        number++
        continue
    }
    other++
}
print(letter)
print(blank)
print(number)
print(other)