ryanmcdermott · schoenwaldnils · Jan 6, 2017 · Jan 7, 2017 · Jan 7, 2017 · Jan 7, 2017
diff --git a/README.md b/README.md
@@ -8,8 +8,9 @@
   5. [Classes](#classes)
   6. [Testing](#testing)
   7. [Concurrency](#concurrency)
-  8. [Formatting](#formatting)
-  9. [Comments](#comments)
+  8. [Error Handling](#error-handling)
+  9. [Formatting](#formatting)
+  10. [Comments](#comments)
 
 ## Introduction
 ![Humorous image of software quality estimation as a count of how many expletives
@@ -52,11 +53,10 @@ var yearMonthDay = moment().format('YYYY/MM/DD');
 ```
 **[⬆ back to top](#table-of-contents)**
 
-### Use ES6 constants when variable values do not change
-In the bad example, the variable can be changed.
-When you declare a constant, the variable should stay
-the same throughout the program.
-
+### Use ES6 constants when variable will not be reassigned
+In the bad example, the variable can be reassigned.
+When you declare a constant, the variable can only be altered.
+If you want to reassign a variable use `let`.
 
 **Bad:**
 ```javascript
@@ -66,6 +66,11 @@ var FIRST_US_PRESIDENT = "George Washington";
 **Good**:
 ```javascript
 const FIRST_US_PRESIDENT = "George Washington";
+
+let CURRENT_US_PRESIDENT = "Donald Trump";
+if (bool) {
+  CURRENT_US_PRESIDENT = "somone else";
+}
 ```
 **[⬆ back to top](#table-of-contents)**
 
@@ -379,7 +384,7 @@ function parseBetterJSAlternative(code) {
   let ast = lexer(tokens);
   ast.forEach((node) => {
     // parse...
-  })  
+  })
 }
 ```
 **[⬆ back to top](#table-of-contents)**
@@ -508,7 +513,7 @@ function createMenu(config) {
     cancellable: true
   }, config);
 
-  // config now equals: {title: "Order", body: "Bar", buttonText: "Send", cancellable: true}
+  // config now equals: {title: "Foo", body: "Bar", buttonText: "Baz", cancellable: true}
   // ...
 }
 
@@ -767,7 +772,7 @@ class Airplane {
         return getMaxAltitude() - getPassengerCount();
       case 'Air Force One':
         return getMaxAltitude();
-      case 'Cesna':
+      case 'Cessna':
         return getMaxAltitude() - getFuelExpenditure();
     }
   }
@@ -794,7 +799,7 @@ class AirForceOne extends Airplane {
   }
 }
 
-class Cesna extends Airplane {
+class Cessna extends Airplane {
   //...
   getCruisingAltitude() {
     return getMaxAltitude() - getFuelExpenditure();
@@ -1318,7 +1323,7 @@ class DOMTraverser {
 
 let $ = new DOMTraverser({
   rootNode: document.getElementsByTagName('body'),
-  options: {  
+  options: {
     animationModule: function() {}
   }
 });
@@ -1793,6 +1798,79 @@ async function getCleanCodeArticle() {
 **[⬆ back to top](#table-of-contents)**
 
 
+## **Error Handling**
+Thrown errors are a good thing! They mean the runtime has successfully
+identified when something in your program has gone wrong and it's letting
+you know by stopping function execution on the current stack, killing the
+process (in Node), and notifying you in the console with a stack trace.
+
+### Don't ignore caught errors
+Doing nothing with a caught error doesn't give you the ability to ever fix
+or react to said error. Logging the error to the console (`console.log`)
+isn't much better as often times it can get lost in a sea of things printed
+to the console. If you wrap any bit of code in a `try/catch` it means you
+think an error may occur there and therefore you should have a plan,
+or create a code path, for when it occurs.
+
+**Bad:**
+```javascript
+try {
+  functionThatMightThrow();
+} catch (error) {
+  console.log(error);
+}
+```
+
+**Good:**
+```javascript
+try {
+  functionThatMightThrow();
+} catch (error) {
+  // One option (more noisy than console.log):
+  console.error(error);
+  // Another option:
+  notifyUserOfError(error);
+  // Another option:
+  reportErrorToService(error);
+  // OR do all three!
+}
+```
+
+### Don't ignore rejected promises
+For the same reason you shouldn't ignore caught errors
+from `try/catch`.
+
+**Bad:**
+```javascript
+getdata()
+.then(data => {
+  functionThatMightThrow(data);
+})
+.catch(error => {
+  console.log(error);
+});
+```
+
+**Good:**
+```javascript
+getdata()
+.then(data => {
+  functionThatMightThrow(data);
+})
+.catch(error => {
+  // One option (more noisy than console.log):
+  console.error(error);
+  // Another option:
+  notifyUserOfError(error);
+  // Another option:
+  reportErrorToService(error);
+  // OR do all three!
+});
+```
+
+**[⬆ back to top](#table-of-contents)**
+
+
 ## **Formatting**
 Formatting is subjective. Like many rules herein, there is no hard and fast
 rule that you must follow. The main point is DO NOT ARGUE over formatting.