 Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program  and write your own code 
###  Problem Explanation:
You will create a program that will find the missing letter from a string and return it. If there is no missing letter, the program should return undefined. There is currently no test case for the string missing more than one letter, but if there was one, recursion would be used. Also, the letters are always provided in order so there is no need to sort them.
#### Relevant Links
*<ahref='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String'target='_blank'rel='nofollow'>String global object</a>
You will need to figure out where the missing letter is, along with handling the case that there is not missing letter as it needs an specific return value.
* Code of encountered character is stored in **code**.
* It is checked if code of current character is the expected one (no characters are skipped) by using the logic - `code of current character = code of first character + number of iterations`.
* If a character is missing, the missing character is found and the final string is returned.
*`undefined` is returned if there is no missing character in the string.
#### Relevant Links
*<ahref='http://forum.freecodecamp.com/t/javascript-for-loop/14666s-Explained'target='_blank'rel='nofollow'>JS For Loops Explained</a>
##  NOTES FOR CONTRIBUTIONS:
*  **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.
* Add an explanation of your solution.
* Categorize the solution in one of the following categories — **Basic**, **Intermediate** and **Advanced**. 