Express API

• Look at https://github.com/kurmasz-SampleCode/CIS371-SampleCode/tree/master/JavaScript/blogAPI
• Similar to the expressMVC example with a few changes
  • Port is changed to 3001. (Needs to run on a different port than React server)
  • bodyParser is JSON instead of urlencoded
  • Using cors package (instead of just adding the header)
• I wrote a single method to automatically create all CRUD routes
  • Makes it easier to add more resources later (e.g., blog posts)
  • Additional resources take one line. (Or can re-use method in other apps)
• When calling res.send with objects, they are automatically converted to JSON
• AuthorDB.create returns the id of the newly created object
  • The lastID variable is unique to Sqlite3.
• Notice that this.db.run uses the function syntax, not the () => syntax. This is because the () => syntax won’t set up the this variable properly.
  • This is one of the few cases where the difference between function and () => syntax matters.

More Verbs

• Complete list of HTTP verbs:
  • GET
  • HEAD
  • POST
  • PUT
  • DELETE
  • CONNECT
  • OPTIONS
  • TRACE
  • PATCH
• Typical API verbs
  • GET
  • POST: Post new data
  • PUT: Put replacement data
  • PATCH: Patch an entry (i.e., only change part of it.)
  • DELETE
• Use PUT when you are sending the entire object to be replaced.
  • This is what blogAPI does.
• Use PATCH if you are sending only the fields that are changing.
• Remember, only GET and POST can be sent directly from a web page.
  • PUT, PATH, DELETE etc, can only be sent using JavaScript.

Status Codes

• 500 “Internal Server Error.” If you server code crashes. For example:
  • Null Pointer Exception
  • Divide by Zero error.
  • Other unhandled exception.
  • (Rails sends a 500 if a DB command fails because you didn’t check that all constraints were satisfied first.)
• 422 “Unprocessable Entry”: Data is well-formed, but invalid. (For example, the Author’s email is not unique)
• 204 “No Content” Used for calls like update and delete where there isn’t anything else to say but “success”
• Look at API.jsx.
  • Notice that it checks explicitly for status.
  • API calls return a promise.
  • Anything returned is passed to the then block.
  • If a throw is called anywhere, the catch block is run.
  • See Authors.jsx in react-blog-complete