？？Repeat a string repeat a string -- Freecodecamp

Repeat a given string (first argument) num times (second argument). Return an empty string if num is not a positive number.
TEST
repeatStringNumTimes("", 3) should return "*".
repeatStringNumTimes("abc", 3) should return "abcabcabc".
repeatStringNumTimes("abc", 4) should return "abcabcabcabc".
repeatStringNumTimes("abc", 1) should return "abc".
repeatStringNumTimes("", 8) should return "********".
repeatStringNumTimes("abc", -2) should return "".

！问题：数组与字符一些方法弄混

//方法1
function repeatStringNumTimes(str, num) {
        var newStr = '';
        while(num>0){
            newStr += str;
            num--;
        }
        return newStr;
}
console.log(repeatStringNumTimes("abc", 3));```

##??return str + repeatStringNumTimes(str,num-1);能不能直接修改为repeatStringNumTimes(str,num);？？

//方法2：递归
function repeatStringNumTimes(str,num){
if(num<0)
return '';
if(num===1)
return str;
else
return str + repeatStringNumTimes(str,num-1);
}
console.log(repeatStringNumTimes("abc", 3));```

//方法3: str.repeat()
function repeatStringNumTimes(str,num){
        return num > 0 ? str.repeat(num) : '';
    }
console.log(repeatStringNumTimes("abc", 3));```