 There are a couple of new technologies you're going to see a lot of in this course. Those technologies are the Fetch API and Promises. Promises make asynchronous programming much easier. The Fetch API is a replacement for XML HTTP request built on Promises. In this example, we're getting a JSON file, parsing it, and capturing any exceptions that occur. This is much simpler than writing a collection of event handlers and simplifies code reuse. The key here is the then function. It takes a function reference and waits for the previous operation to complete before calling the function. If any errors occur, it transfers execution to the catch at the end. We're going to use a lot of anonymous functions in this course. You can use the same function declarations you've always used, or use the new ES2015 fat arrow syntax to declare a function. The new syntax takes a list of parameters on the left, the equals greater than arrow, and a code body on the right. Take a moment to look at this shorthand as we will be using it frequently. Using fat arrow functions lets us rewrite the first example more concisely. We call Fetch, pass the result to a function, and we catch any exceptions with a second function. That probably went by quickly, so take a moment to try these in your browser's console. They work in most modern browsers, but check your favorite source for fetch and promises support. Open the browser's console and type in this quick fetch sample. It gets index.html in the local directory and shows the result. Try it with and without an index.html file. You can find this sample in the Core Technologies Lab folder under fetch.txt. Let's try this sample that retrieves a JSON file. Just change the file name to animals.json and the response decoder from text to JSON all lowercase. This time, it fetches animals.json, which is in the Core Technologies folder, and decodes the JSON. And that's it. Don't worry if that went by quickly. We'll take a deeper dive into fetch and promises in a bit. Please take a few minutes and experiment with these examples before moving on to the service worker. So, that's it. Thank you. Thank you. Bye. Bye. Bye. Bye. Bye.