update readme to have brief functions intro

README.md

@@ -9,12 +9,20 @@ In this code-along, we will practice working with control flow in JavaScript.
 3. Practice writing `switch` statements.
 
 ## Introduction
-You have been hired as a contractor for Scuber, a burgeoning startup that helps busy parents transport their children to and from all of their activities on scooters.
+You have been hired as a contractor for Scuber, a burgeoning startup that helps
+busy parents transport their children to and from all of their activities on
+scooters.
 
-Scuber's drivers charge their passengers a variable amount based on how far they need to travel. Modify the `index.js` file to ensure that Scuber's drivers are properly telling their passengers how much the ride will cost.
+Scuber's drivers charge their passengers a variable amount based on how far
+they need to travel. Modify the `index.js` file to ensure that Scuber's drivers
+are properly telling their passengers how much the ride will cost.
 
 ## Read the Tests
-We know that you do not have much experience with testing, so that is why it is very important for you to read the instructions in this and every lab. That being said, reading the tests can often provide supplemental guidance on how to complete a lab. Let's take a look at the first test for this lab together:
+We know that you do not have much experience with testing, so that is why it is
+very important for you to read the instructions in this and every lab. That
+being said, reading the tests can often provide supplemental guidance on how to
+complete a lab. Let's take a look at the first test for this lab together:
+
 ```js
 describe('index.js', function () {
   describe('scuberGreetingForFeet()', function () {
@@ -27,33 +35,109 @@ describe('index.js', function () {
 });
 ```
 
-Ok so all of the fancy `describe` words are just there to organize the requirements, and provide a mechanism for what each function should do. By reading the text inside of the `describe` words, we can see that there is some function that should give customers a free sample, where the first 400 feet are free. Then in the next line we see a function called `scuberGreetingForFeet` being executed with `199` passed through as an argument to the function. Executing the `scuberGreetingForFeet` function with the argument should return `"This one is on me!"`.
+Okay, so all of the fancy `describe` words are just there to organize the
+requirements, and provide a mechanism for what each function should do. By
+reading the text inside of the `describe` words, we can see that there is some
+function that should give customers a free sample, where the first 400 feet are
+free. Then in the next line we see a function called `scuberGreetingForFeet`
+being executed with `199` passed through as an argument to the function.
+Executing the `scuberGreetingForFeet` function with the argument should return
+`"This one is on me!"`.
 
-If we run the tests with the `learn` command, we see that `scuberGreetingForFeet` is not defined. We can fix this by writing a function `scuberGreetingForFeet` in the index.js file. The big insight is that the tests in the indexTest.js file are calling the functions that we write the index.js file. These tests pass arguments to our function. When this test passes an argument of `199` to our function, the `scuberGreetingForFeet` function should return `"This one is on me!"`. That makes sense, considering the text in the `describe` and `it` functions say that the first 400 feet should be free. That `199` must be indicating the distance in feet of the requested ride.
+If we run the tests with the `learn` command, we see that
+`scuberGreetingForFeet` is not defined. We can fix this by writing a function
+`scuberGreetingForFeet` in the `index.js` file.
 
-So reading tests are essentially like reading the instructions. It's something, we may have avoided for much of our lives, but when it comes to programming, tests fill in the picture of the goal we are trying to accomplish. They run mini-experiments on our code and help us better understand our code and the problem we are solving.
+...but wait! We haven't gone over writing functions yet!  We will tackle the
+details of function writing in an upcoming lab. For now, briefly, a function
+declaration is written like so:
 
-## Instructions
-There are three functions you need to fill in:
-* `scuberGreetingForFeet()` — Use `if` and `else if` statements to return the correct greeting based on the distance the passenger desires to travel.
-* `ternaryCheckCity()` — Use a ternary operator to return the correct response based on the desired destination of the passenger.
-* `switchOnCharmFromTip()` — Use a `switch` statement to return a different response based on the generosity of the passenger's tip.
+```js
+function addFive(someNumber) {
+  //everything I want my function to do I put inside these curly braces
+  //in this example, I want my function, addFive, to add 5 to any number I pass in (someNumber)
+  let result = someNumber + 5;
+  //at the end, if I want my function to return something, I need to state it:
+  return result
+}
+
+//once our function is declared, we can call addFive, passing in values as arguments
+//in the example test early, scuberGreetingForFeet(199) calls the function with 199 as the argument
+
+addFive(10);
+//returns 15
+addFive(20);
+//returns 25
+addFive(addFive(5));
+//returns 15!! In this case, the return value of addFive(5), 10, is passed in as the argument to the outer addFive, returning 15
+```
 
-***NOTE***: Remember, each time you save the `index.js` file the test suite in your browser will automatically re-run itself and push the results to Learn. When all of the tests are passing at the end of the lab, the `Run Local Tests` light on the Learn.co lesson page will turn green.
+So, looking back at our test example, `scuberGreetingForFeet(199)` is calling
+the function `scuberGreetingForFeet`, and passing in the value `199` as the
+argument.  When we write this function, we need to write the logic inside the
+curly braces to pass our tests and return the result:
+
+```js
+function scuberGreetingForFeet(someValue) {
+  //this is where we can use conditionals given our argument, someValue
+  //don't forget to return whatever the result is!
+}
+```
+
+The big insight from reading the example test above is that the tests in the
+`indexTest.js` file are calling the functions that we write inside the
+`index.js` file. These tests pass arguments to our function. When this test
+passes an argument of `199` to our function, the `scuberGreetingForFeet`
+function should return `"This one is on me!"`. That makes sense, considering
+the text in the `describe` and `it` functions say that the first 400 feet
+should be free. That `199` must be indicating the distance in feet of the
+requested ride.
+
+So reading tests are essentially like reading the instructions. It's something
+we may have avoided for much of our lives, but when it comes to programming,
+tests fill in the picture of the goal we are trying to accomplish. They run
+mini-experiments on our code and help us better understand our code and the
+problem we are solving.
+
+## Instructions
+There are three functions you need to declare and fill in:
+* `scuberGreetingForFeet()` — Use `if` and `else if` statements to return the
+correct greeting based on the distance the passenger desires to travel.
+* `ternaryCheckCity()` — Use a ternary operator to return the correct response
+based on the desired destination of the passenger.
+* `switchOnCharmFromTip()` — Use a `switch` statement to return a different
+response based on the generosity of the passenger's tip.
+
+***NOTE***: Remember, each time you save the `index.js` file the test suite in
+your browser will automatically re-run itself and push the results to Learn.
+When all of the tests are passing at the end of the lab, the `Run Local Tests`
+light on the Learn.co lesson page will turn green.
+
+***NOTE***: Beware a gotcha! In JavaScript, you cannot express the concept of
+'between' in the following way:
 
-***NOTE***: Beware a gotcha! In JavaScript, you cannot express the concept of 'between' in the following way:
 ```js
 2 < 5 < 4
 // => true
 ```
 
-It seems like that expression should evaluate to `false` because `5` is not less than `4`. However, we're forgetting about the order of operations — let's think about how the JavaScript engine evaluates that expression. First, the engine compares `2 < 5`, which evaluates to `true`. At that point, it's as though the value `true` has replaced `2 < 5` in the expression, resulting in `true < 4`. The engine sees that we're trying to compare a non-number (`true`) against a number (`4`), and under the hood it converts `true` into a number:
+It seems like that expression should evaluate to `false` because `5` is not
+less than `4`. However, we're forgetting about the order of operations — let's
+think about how the JavaScript engine evaluates that expression. First, the
+engine compares `2 < 5`, which evaluates to `true`. At that point, it's as
+though the value `true` has replaced `2 < 5` in the expression, resulting in
+`true < 4`. The engine sees that we're trying to compare a non-number (`true`)
+against a number (`4`), and under the hood it converts `true` into a number:
+
 ```js
 Number(true);
 // => 1
 ```
 
-That leaves us with `1 < 4`, which the JavaScript engine correctly evaluates to `true`. Can you figure out how to properly evaluate whether `5` is greater than `2` **AND** `5` is less than `4`? Ponder that as you work through the assignment below.
+That leaves us with `1 < 4`, which the JavaScript engine correctly evaluates to
+`true`. Can you figure out how to properly evaluate whether `5` is greater than
+`2` **AND** `5` is less than `4` using logic operators? Ponder that as you work
+through the assignment,.
 
 Good luck!