JadenCasing

/*
This was my first kata on codewars, excluding the entrance kata.
The kata gave me quite a challenge and I enjoyed working through it.
There is something that I still don't understand about this function
that perplexed me.  I created the code fine with a test string, but
upon removing the test string and trying to bring in the parameter
I noticed it would always show up as undefined.  I stumbled upon "this", 
but unfortunately still do not have a grasp on why it was relevant in this
instance.  I feel that it must have something to do with the way the function
is setup.  I know that this is a function expression because I am storing it into 
a variable for the declaration.  I also understand that it is an extension
of String.prototype.  I feel that something about it being a function expression
or having something to do with the fact that it was an extension of the String method.
I will look into this and see where and why it comes into play.  

I used the tools available to me to complete this kada.  I know that some of the other 
submissions used different ways to get the job done.  I will come back and rewrite this as
I learn more as well to see if I can make it better.
*/
String.prototype.toJadenCase = function () {
  //split the string into an array of substrings using split function with space as the separator
  var jadenStringArray = this.split(" ");
  //defining my final result at the top so it is in scope of all loops.
  var finalResult = "";
   //use foreach loop to run through each of the substrings
  for (var i = 0; i < jadenStringArray.length; i++){
      //split the substrings into arrays.
      var txt = jadenStringArray[i].split("");
      //setup the result within scope to be used.
      var result = "";
      //Loop through the letters of each word.
        for (var ii = 0; ii < txt.length; ii++){
        // if the letter is the first letter
         if (ii === 0){
         //change the case to upper case
         txt[ii] = txt[ii].toUpperCase();
         //save the word we created
         jadenStringArray[i] = txt.join("");
         }//end if
        }//end for letters iteration
  }//end for word iterations
    //join the strings back together as a string.
    finalResult += jadenStringArray.join(" ");
    //return the finalResult back to the user
  return finalResult
};// end function toJadenCase