API Routing with Express

Note: This is the 2nd post of a series of post about Building APIs With Express.

Based on my last post about Making APIs with Node and Express I'll continue developing over the generated code.

So, I leaved the basement for my TODO API prepared. Now it's time to work in the different endpoints and HTTP verbs/methods that this API is going to use.

/v1/tasks

I'm going to start building my API's endpoints with Tasks Collection.

[GET] /v1/tasks

First thing I need is to GET the list of tasks from my so innovative TODO API and I think that the best way to build it is by creating a new isolated express router instance.

src/v1/tasks.js

const router = require('express').Router()

/**
 * TODO: Store data in DB.
 */
let tasks = [  
  {
    description: 'Another task',
    isDone: false,
    createdAt: Date.now()
  }
]

router.route('/')

  .get((req, res, next) => {
    return res.json(tasks)
  })

module.exports = router  

Easy peasy! Now I need to mount that router on my API, I'm going to remove the old Let's TODO! message:

src/v1/index.js

const router = require('express').Router()  
const tasks = require('./tasks')

router.use('/tasks', tasks)

module.exports = router  

Let's try the new endpoint (Now that I have implemented yarn I can run the server with `yarn startinstead ofnpm start`):

curl -X GET localhost:3000/v1/tasks  
[
   {
      "createdAt" : 1481985039988,
      "isDone" : false,
      "description" : "Another task"
   }
]

Note: It's needed to restart the server if there has been changes in the code while it is running to see the changes.

Now I'll continue with the creation of a new task

[POST] /v1/tasks

It should be in the same router instance the GET method is. This time I'll need a new middleware to parse correctly the request body, body-parser (this time I'll install it with Yarn).

yarn add body-parser  

Note: Same as execute npm i -S body-parser

And now it needs to be attached to the app

src/index.js

const express = require('express')  
const logger = require('morgan')  
const bodyParser = require('body-parser')  
const app = express()  
const v1 = require('./v1')

/**
 * Middlewares
 */
app.use(logger('dev'))  
app.use(bodyParser.json())  
app.use(bodyParser.urlencoded({ extended: true }))

...

Note: It will inject data from the request into req.body.

And now the request handler.

src/v1/tasks.js

...

router.route('/')

  .get((req, res, next) => {
    return res.json(tasks)
  })

  .post((req, res, next) => {
    const newTask = req.body

    newTask.createdAt = Date.now()
    newTask.isDone = false
    tasks.push(newTask)

    return res.status(201).json(newTask)
  })

module.exports = router  

Note: Take advantage of the HTTP status codes.

Done, let's try again with a POST request this time:

curl -X POST -H "Content-Type: application/json" --data '{"description": "Also another task more"}' localhost:3000/v1/tasks  
{"description":"Also another task more","createdAt":1481986821539}

curl -X GET localhost:3000/v1/tasks  
[
   {
      "createdAt" : 1481986807819,
      "isDone" : false,
      "description" : "Another task"
   },
   {
      "createdAt" : 1481986821539,
      "isDone" : false,
      "description" : "Also another task more"
   }
]

Time to delete! Due this is an endpoint pointing a collection when it receives a DELETE request it should delete all items of the collection.

[DELETE] /v1/tasks

src/v1/tasks.js

...

  .post((req, res, next) => {
    const newTask = req.body

    newTask.createdAt = Date.now()
    tasks.push(newTask)

    return res.json(newTask)
  })

  .delete((req, res, next) => {
    tasks = []

    res.status(204).end()
  })

module.exports = router  

Delete all the things!

curl -X DELETE -i localhost:3000/v1/tasks

HTTP/1.1 204 No Content  
X-Powered-By: Express  
ETag: W/"2-11FxOYiYfpMxmANj4kGJzg"  
Date: Sat, 17 Dec 2016 17:13:07 GMT  
Connection: keep-alive  

I am done with this endpoint.

/v1/tasks/:taskId

Now it's time to handle the single task endpoint. Here I'm going to take advantage of an Express feature to parse URLs, for this case, to treat a segment of the URL as a parameter and assigning it the name taskId.

taskId param

I am going to define a new param for the tasks router to get a certain task passing the task ID in the URL.

src/v1/tasks.js

...

router.route('/')

...

router.param('taskId', (req, res, next, id) => {  
  const task = tasks[id]
  let err

  if (!task) {
    err = new Error('Task not found')
    err.status = 404
  } else {
    req.task = task
  }

  return next(err)
})

module.exports = router  

[GET] /v1/tasks/:taskId

Then I only need to reply with the found task in a new endpoint listening to any request aimed to /v1/tasks/:taskId meaning by :taskId whatever comes after the slash (IE: /v1/tasks/my-task-id OR /v1/tasks/01234).

src/v1/tasks.js

...

router.param('taskId', (req, res, next, id) => {  
  ...
})


router.route('/:taskId')

  .get((req, res, next) => {
    return res.json(req.task)
  })

module.exports = router  

Let's try it

curl -X GET localhost:3000/v1/tasks/0  
{
   "description" : "Another task",
   "isDone" : false,
   "createdAt" : 1481996187751
}

curl -X GET -i localhost:3000/v1/tasks/1234

HTTP/1.1 404 Not Found  
X-Powered-By: Express  
Content-Type: application/json; charset=utf-8  
Content-Length: 1082  
ETag: W/"43a-4d6NK29IKrV0B3jSAdQGvA"  
Date: Sat, 17 Dec 2016 17:46:36 GMT  
Connection: keep-alive  
{
   "stack" : "Error: Task not found\n    at router.param (/develop/another-todo-api/src/v1/tasks.js:38:11)\n    at paramCallback (/develop/another-todo-api/node_modules/express/lib/router/index.js:404:7)\n    at param (/develop/another-todo-api/node_modules/express/lib/router/index.js:384:5)\n    at Function.process_params (/develop/another-todo-api/node_modules/express/lib/router/index.js:410:3)\n    at next (/develop/another-todo-api/node_modules/express/lib/router/index.js:271:10)\n    at Function.handle (/develop/another-todo-api/node_modules/express/lib/router/index.js:176:3)\n    at router (/develop/another-todo-api/node_modules/express/lib/router/index.js:46:12)\n    at Layer.handle [as handle_request] (/develop/another-todo-api/node_modules/express/lib/router/layer.js:95:5)\n    at trim_prefix (/develop/another-todo-api/node_modules/express/lib/router/index.js:312:13)\n    at /develop/another-todo-api/node_modules/express/lib/router/index.js:280:7",
   "message" : "Task not found"
}

[POST] /v1/tasks/:taskId

Now it's important to pay atention here because the POST request to a specified resource in an API REST by definition should override completely the resource, meaning that if:
I do a GET to /v1/tasks/0 receiving:

{
   "description" : "Another task",
   "isDone" : false,
   "createdAt" : 1481996187751
}

If I do a POST to /v1/tasks/0 with this data:

{ "isDone": true }

The next time I do a GET to /v1/tasks/0 I'll receive the next response:

{ "isDone": true }

The proper way a client should make a POST to an API resource is by providing all the resource info in the request to avoid the lose of info.

Now go back to code!

src/v1/tasks.js

...
  .post((req, res, next) => {
    const updatedTask = req.body

    tasks[req.params.taskId] = updatedTask

    return res.json(updatedTask)
  })
...

[PATCH] /v1/tasks/:taskId

Now the PATCH request is the one used to update partially a resource in an API REST.

src/v1/tasks.js

...
  .patch((req, res, next) => {
    for (let prop in req.body) {
      tasks[req.params.taskId][prop] = req.body[prop]
    }

    return res.json(tasks[req.params.taskId])
  })
...

Let's try this one with curl:

curl -X PATCH -H "Content-Type: application/json" --data '{"isDone": true}' localhost:3000/v1/tasks/0  
{
   "isDone" : true,
   "description" : "Another task",
   "createdAt" : 1481998868351
}

Oh yeah!

[DELETE] /v1/tasks/:taskId

I think there's no much to explain here, is pretty much the same as the DELETE for the whole collections instead that this one only deletes one resource.

src/v1/tasks.js

...
  .delete((req, res, next) => {
    tasks.splice(req.params.taskId, 1)

    res.status(204).end()
  })
...

End of the route

Well, I think that with this the awesome Another TODO API is completely functional, maybe I should care about that the info isn't being stored anywhere and every time the server stops I lose it all, but that'll be another time!

Comment and check the code on GitHub!