Create a mock API server with node and json-server

During the development lifecycle, we often encounter situations where we need to mock an external API server - either because it's temporarily unavailable (we might be offline) or because it simply wasn't built yet.

Here is how to get one running in no time.

Setup

We'll start by creating a new folder to store the files required for our server:

$ mkdir ApiServer

... and change the current path to that folder:

$ cd ApiServer

JSON Server

We are going to use the json-server npm library. To install JSON Server, globally in your system, run:

$ npm install -g json-server

/usr/local/bin/json-server -> /usr/local/lib/node_modules/json-server/lib/cli/bin.js + json-server@0.15.1 added 237 packages from 128 contributors in 12.542s

Data file

Let's now create a file that will contain the data to be served. Create a data.json file with the following content

{
  "tasks": [
    {
      "id": 1,
      "name": "Buy some milk"
    },
    {
      "id": 2,
      "name": "Renew insurance"
    }
  ]
}

Start server

Let's now start the server:

$ json-server -p 8080 --watch data.json

The console output will look like this:

  \{^_^}/ hi!

  Loading data.json
  Done

  Resources
  http://localhost:8080/tasks

  Home
  http://localhost:8080

  Type s + enter at any time to create a snapshot of the database
  Watching...

Navigate to http://localhost:8080 to see an overview page, or to http://localhost:8080/tasks to retrieve the tasks.

json-server has loads of other options that you might find useful:

$ json-server --help

json-server [options] 

Options:
  --config, -c Path to config file [default: "json-server.json"]
  --port, -p Set port [default: 3000]
  --host, -H Set host [default: "localhost"]
  --watch, -w Watch file(s) [boolean]
  --routes, -r Path to routes file
  --middlewares, -m Paths to middleware files [array]
  --static, -s Set static files directory
  --read-only, --ro Allow only GET requests [boolean]
  --no-cors, --nc Disable Cross-Origin Resource Sharing [boolean]
  --no-gzip, --ng Disable GZIP Content-Encoding [boolean]
  --snapshots, -S Set snapshots directory [default: "."]
  --delay, -d Add delay to responses (ms)
  --id, -i Set database id property (e.g. _id) [default: "id"]
  --foreignKeySuffix, --fks Set foreign key suffix (e.g. _id as in post_id)
                                                                 [default: "Id"]
  --quiet, -q Suppress log messages from output [boolean]
  --help, -h Show help [boolean]
  --version, -v Show version number [boolean]

Examples:
  json-server db.json
  json-server file.js
  json-server http://example.com/db.json

https://github.com/typicode/json-server

That's it. You can now consume the contents of data.json using simple local requests.