var str ="abcABCadDGSDVBSDVDSVdavver"
var count=0
for(let i = 0;i<str.length;i++){
    var char = str[i].charCodeAt()
    if(char>=65&&char<=90){
        count++
    }
}
console.log(count+'个')
//大写字母共15个

var str ="abcABCadDGSDVBSDVDSVdavver"
var count=0
for(let i = 0;i<str.length;i++){
    var char = str[i].charCodeAt()
    if(char>=97&&char<=122){
        count++
    }
}
console.log(count+'个')
//小写字母共11个