fundamentals-3.md

Functions

Things are about to get really exciting. So far you have been writing an impressive amount of code to solve various problems but that code has not been as useful as it could be. Imagine taking one of your scripts and bundling it into a little package that you could use over and over again without having to rewrite or change the code. That's the power of functions and they're used constantly in JavaScript.

1. Another lengthy MDN article is a good place to start. Pay special attention to the sections on 'Function Scope'. Scope is one topic that commonly trips up both beginner and intermediate coders so it pays to spend some time with it up front.
2. Read this article about return values.
3. Next, read this one from Javascript.info. We've mentioned this before, but JavaScript has changed a bit over the years and functions have recently received some innovation. This article covers one of the more useful new abilities: 'default parameters'. (NOTE: The last "task" at the end of this lesson uses loops, which you will learn about in the next lesson. Don't worry about that one.)
4. Finally, read one more article about functions in Javascript that will give you a little more context. Another relatively new feature in modern JavaScript is the arrow function which is introduced in this article. Arrow functions are useful, but not incredibly crucial so don't worry about them too much just yet. We include them here because you are likely to encounter them as you move forward, and it's better that you have at least some idea of what you're looking at whenever they crop up.

Practice

Let's write some functions! Write these in the script tag of a skeleton html file. If you've forgotten how to set it up, review the instructions from fundamentals 1.

For now just write each function and test the output with console.log.

1. Write a function called add7 that takes one number and returns that number + 7.
2. Write a function called multiply that takes 2 numbers and returns their product.
3. Write a function called capitalize that takes a string and returns that string with only the first letter capitalized. Make sure that it can take strings that are lowercase, UPPERCASE or BoTh.
4. Write a function called lastLetter that takes a string and returns the very last letter of that string:
   1. lastLetter("abcd") should return "d"