Day 7 gave us the endpoint: the address a request goes to. Today is what happens on the other side of that address. A route pairs a path with a handler. The path is the pattern, the handler is the code. GET /tasks runs the code that lists tasks. POST /tasks runs the code that creates one. GET /tasks/12 runs the code that loads task number 12. Same path, different method, different handler. That's why the CRUD operations from yesterday can share one endpoint. Routes can hold variables. /tasks/12 and /tasks/13 both match the pattern /tasks/:id. The server pulls out the id and passes it to the handler. Quick check: A request comes in as DELETE /tasks/12. In plain words, what should the matching handler do? ## SPOKEN LINES - You tap a friend's profile and land on the settings screen instead. The address bar says users, 4521, and the server sent back the wrong page. One rule on the server pointed that path at the wrong code. - - ROUTE - - A route is a rule on the server that matches a path to the code that handles it. The server keeps a list of them. A request comes in, the path is checked against the list, and the matching code runs. - - The cart path runs the cart code, users 4521 loads one profile, and orders 88 pulls up a single order. - - So a route is the path that sends a request to the right code. Tomorrow: Framework, the ready-made structure most apps are built inside. ## NEXT Day 15: Framework

Create, Read, Update, Delete. Four operations, and they cover most of what an app does with its database (day 4). They line up with HTTP methods from day 11: Create is usually a POST. Read is a GET. Update is a PUT or PATCH. Delete is a DELETE. So "add a task to my list" becomes a POST to the tasks endpoint with a JSON body describing the task. "Show my tasks" is a GET to the same endpoint. "Mark it done" is a PATCH. "Remove it" is a DELETE. When someone says they built a CRUD app, they mean an app whose main job is letting users manage records like that. Quick check: You change your profile picture. Which of the four is that? ## SPOKEN LINES - The grocery list you deleted on your phone is back the next time you open the app on your laptop. One of four basic actions never reached the database, and now your notes are lying to you. Every app you own is built on those same four actions. - - CRUD - - CRUD stands for Create, Read, Update, Delete. Those are the four things an app does with the data in its database. - - Posting a photo is create, scrolling the feed is read, editing the caption is update, and the trash icon is delete. - - So CRUD is the four basic things an app does with its data. Tomorrow: Route, how the server knows which code should handle your request. ## NEXT Day 14: Route

Commits form a chain. Each new commit points back at the one before it. A branch is a name for a chain, pointing at its newest commit. Every repository starts with one branch. Most teams call it main. When you create a second branch, nothing is duplicated on disk. Git just adds a new name pointing at the same commit main is on. From then on, commits you make on the new branch move that name forward, and main stays where it was. That's why branches are cheap. Making one takes a fraction of a second, so people make them for everything: a feature, a bug fix, an experiment they'll throw away. Naming helps. fix-checkout-total says more than test2. Quick check: You're on a branch called add-dark-mode and you make three commits. Has main changed? ## SPOKEN LINES - Halfway through a rewrite in the live code, a customer reports the checkout page is gone. You needed a copy to work on while the original stayed clean. - - BRANCH - - A branch is a separate line of commits. The main branch is the version that works, and a new branch splits off from it so you can build for a week while main stays untouched. - - Dark mode gets its own branch, a new checkout page gets its own branch, and a bug fix that takes 20 minutes gets one too. - - So a branch is a separate line of development inside the same project. Tomorrow: Merge, how the branch gets back into main. ## NEXT Day 23: Merge

Git tracks changes. A commit is the unit it tracks them in. The flow looks like this: 1. You edit some files in the repository. 2. 2. You pick which of those changes belong together (Git calls this staging). 3. 3. You commit them with a message. Git now has a permanent record: which files changed, which lines, who did it, when, and the message. The message is the part beginners skip. "update" and "fix stuff" tell you nothing a month later. "Return 404 when the user id doesn't exist" tells you exactly what happened, and it even ties back to the status codes from Day 10. A useful rule: if you can't describe the change in one line, it's probably two commits. Quick check: You fixed a typo on the home page and also rewrote the signup form. One commit or two? ## SPOKEN LINES - You broke the login button somewhere in the last three hours. In a Google Doc you would open version history and step back. - - COMMIT - - A commit is a saved snapshot of your code changes. You change a few files, write a short note about what you did, and Git stores the snapshot with your name and the time. - - One commit says fix login button on mobile, the next says add dark mode toggle, and the one from last Tuesday says remove old checkout page. - - So a commit is a save point for your code with a note attached. Tomorrow: Branch, a separate line of work that keeps main safe. ## NEXT Day 22: Branch

Git turns a plain folder into the repository from yesterday. You run git init in a folder, and from then on Git can track it. You make changes, tell Git which ones to record, and it saves a snapshot with your name, the time, and a message. That snapshot is a commit, tomorrow's word. Git's history is a chain of those snapshots. You can compare any two, roll back to any one, or start a separate line of changes and merge it in later. Days 21 to 24 cover those pieces one at a time. Git is local by default. Nothing leaves your machine until you push to a remote like GitHub. That's why you can work on a plane and sync later. Quick check: Git and GitHub. Which one is the tool on your computer, and which one is the website? ## SPOKEN LINES - Two of you edit the same file on the same afternoon. Whoever saves last wins, and the other person's hour of work is gone. - - GIT - - Git is a version control system. It watches your project folder, and when you tell it to, it records a snapshot with a note about what changed. - - You can undo a change from six months ago, two people can edit the same project at once, and a risky idea can live in its own line and get thrown away. - - So Git is the system that tracks every change to your code. Tomorrow: Commit, the snapshot Git takes when you tell it to. ## NEXT Day 21: Commit