To Upper Case (freeCodeCamp challenge)

to_upper_case.txt

/*
Return the provided string with the first letter of each word capitalized. 
Make sure the rest of the word is in lower case.
*/

function titleCase(str) {
  
function toUpper (word){                                      //https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace
    return word.toUpperCase();                                //"The important thing here is that additional operations are needed on the matched item before
  }                                                           // it is given back as a replacement. The replacement function accepts the matched snippet as its parameter, and uses it to transform the case"

  return str.toLowerCase().replace(/(^|\s)\S/g, toUpper);     //lowercase the string, then make a replacement using .replace method.
}                                                             //here its parameters are regexp and function. RegExp pattern here matches
titleCase("I'm a litTle tea pot");                            // \S - a single character other than white space, at the beginning of a string ^ or |
                                                              // after a single white space character \s
                                                              // g is a flag (regExp parameter). Means global match; tells to find all matches rather than stopping after the first match