str (first argument) for num times (second argument). Return an empty string if num is not a positive number.
Remember to use Read-Search-Ask if you get stuck. Write your own code.
repeatStringNumTimes("*", 3) should return "***".
    testString: assert(repeatStringNumTimes("*", 3) === "***");
  - text: repeatStringNumTimes("abc", 3) should return "abcabcabc".
    testString: assert(repeatStringNumTimes("abc", 3) === "abcabcabc");
  - text: repeatStringNumTimes("abc", 4) should return "abcabcabcabc".
    testString: assert(repeatStringNumTimes("abc", 4) === "abcabcabcabc");
  - text: repeatStringNumTimes("abc", 1) should return "abc".
    testString: assert(repeatStringNumTimes("abc", 1) === "abc");
  - text: repeatStringNumTimes("*", 8) should return "********".
    testString: assert(repeatStringNumTimes("*", 8) === "********");
  - text: repeatStringNumTimes("abc", -2) should return "".
    testString: assert(repeatStringNumTimes("abc", -2) === "");
  - text: The built-in repeat() method should not be used.
    testString: assert(!/\.repeat/g.test(code));
  - text:  repeatStringNumTimes("abc", 0) should return "".
    testString: assert(repeatStringNumTimes("abc", 0) === "");
    
```