Check out example codes for "convert all strings in vector to lowercase or uppercase c++". It will help you in understanding the concepts better.

Code Example 1

for(std::string &s : stringVector){
    std::transform(s.begin(), s.end(), s.begin(), 
        [](char c){ return std::toupper(c); }); // for lowercase change "toupper" -> "tolower" 
}

Learn ReactJs, React Native from akashmittal.com