ZetCode

JSON Server tutorial

last modified July 7, 2020

JSON Server tutorial introduces the JavaScript json-server library, which can be used to create fake REST API.

JSON server

The json-server is a JavaScript library to create testing REST API.

JSON Server installation

First, we create a project directory an install the json-server module.

$ mkdir json-server-lib
$ cd json-server-lib
$ npm init -y
$ npm i -g json-server

The JSON server module is installed globally with npm.

$ npm install axios

In addition, we install the axios module, which is a promise-based JavaScript HTTP client.

$ cat package.json
{
  "name": "json-server-lib",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "axios": "^0.18.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}

This is our package.json file.

JSON test data

We have some JSON test data:

users.json
{
  "users": [
    {
      "id": 1,
      "first_name": "Robert",
      "last_name": "Schwartz",
      "email": "rob23@gmail.com"
    },
    {
      "id": 2,
      "first_name": "Lucy",
      "last_name": "Ballmer",
      "email": "lucyb56@gmail.com"
    },
    {
      "id": 3,
      "first_name": "Anna",
      "last_name": "Smith",
      "email": "annasmith23@gmail.com"
    },
    {
      "id": 4,
      "first_name": "Robert",
      "last_name": "Brown",
      "email": "bobbrown432@yahoo.com"
    },
    {
      "id": 5,
      "first_name": "Roger",
      "last_name": "Bacon",
      "email": "rogerbacon12@yahoo.com"
    }
  ]
}    

Starting JSON server

The JSON server is started with the json-server, which we have installed globally.

$ json-server --watch users.json    

The --watch command is used to specify the data for the server.

$ curl localhost:3000/users/3/
{
  "id": 3,
  "first_name": "Anna",
  "last_name": "Smith",
  "email": "annasmith23@gmail.com"
}

With the curl command, we get the user with Id 3.

JSON Server GET request

In the next example we retrieve data with a GET request.

get_request.js
const axios = require('axios');

axios.get('http://localhost:3000/users')
    .then(resp => {
        data = resp.data;
        data.forEach(e => {
            console.log(`${e.first_name}, ${e.last_name}, ${e.email}`);
        });
    })
    .catch(error => {
        console.log(error);
    });    

With the axios module, we get all users as a JSON array and loop through it with forEach().

$ node get_request.js 
Robert, Schwartz, rob23@gmail.com
Lucy, Ballmer, lucyb56@gmail.com
Anna, Smith, annasmith23@gmail.com
Robert, Brown, bobbrown432@yahoo.com
Roger, Bacon, rogerbacon12@yahoo.com

This is the output of the example. We get all users and print their full names and emails.

JSON Server POST request

With a POST request, we create a new user.

post_request.js
const axios = require('axios');

axios.post('http://localhost:3000/users', {
    id: 6,
    first_name: 'Fred',
    last_name: 'Blair',
    email: 'freddyb34@gmail.com'
}).then(resp => {
    console.log(resp.data);
}).catch(error => {
    console.log(error);
});   

A new user is created with axios.

$ node post_request.js 
{ id: 6,
  first_name: 'Fred',
  last_name: 'Blair',
  email: 'freddyb34@gmail.com' }

The server responds with a newly created object.

$ curl localhost:3000/users/6/
{
  "id": 6,
  "first_name": "Fred",
  "last_name": "Blair",
  "email": "freddyb34@gmail.com"
}

We verify the newly created user with the curl command.

JSON Server modify data with PUT request

In the following example we modify data with a PUT request.

put_request.js
const axios = require('axios');

axios.put('http://localhost:3000/users/6/', {
    first_name: 'Fred',
    last_name: 'Blair',
    email: 'freddyb34@yahoo.com'
}).then(resp => {

    console.log(resp.data);
}).catch(error => {

    console.log(error);
});  

In the example, we modify the user's email address.

$ node put_request.js 
{ first_name: 'Fred',
  last_name: 'Blair',
  email: 'freddyb34@yahoo.com',
  id: 6 }

This is the output.

JSON Server DELETE request

In the following example, we show how to delete a user with a DELETE request.

delete_request.js
const axios = require('axios');

axios.delete('http://localhost:3000/users/1/')
    .then(resp => {
        console.log(resp.data)
    }).catch(error => {
        console.log(error);
    });   

In the example, we delete the user with Id 1.

$ node delete_request.js 
{}

The server responds with empty JSON data.

JSON Server sorting data

In the next example, we sort our data.

sort_data.js
const axios = require('axios');

axios.get('http://localhost:3000/users?_sort=last_name&_order=asc')
    .then(resp => {
        data = resp.data;
        data.forEach(e => {
            console.log(`${e.first_name}, ${e.last_name}, ${e.email}`)
        });
    }).catch(error => {
        console.log(error);
    });    

The code example sorts data by the users' last name in ascending order. We use the _sort and _order query parameters.

$ node sort_data.js 
Roger, Bacon, rogerbacon12@yahoo.com
Lucy, Ballmer, lucyb56@gmail.com
Fred, Blair, freddyb34@yahoo.com
Robert, Brown, bobbrown432@yahoo.com
Robert, Schwartz, rob23@gmail.com
Anna, Smith, annasmith23@gmail.com

This is the output.

JSON Server operators

We can use _gte and _lte for getting a specific range of data.

operators.js
const axios = require('axios');

axios.get('http://localhost:3000/users?id_gte=4')
    .then(resp => {
        console.log(resp.data)
    }).catch(error => {
        console.log(error);
    }); 

The code example show users with id greater than or equal to 4.

$ node operators.js 
[ { id: 4,
    first_name: 'Robert',
    last_name: 'Brown',
    email: 'bobbrown432@yahoo.com' },
  { id: '5',
    first_name: 'Roger',
    last_name: 'Bacon',
    email: 'rogerbacon12@yahoo.com' },
  { first_name: 'Fred',
    last_name: 'Blair',
    email: 'freddyb34@yahoo.com',
    id: 6 } ]

This is the output.

JSON Server full text search

A full text search can be performed with the q parameter.

full_text_search.js
const axios = require('axios');

axios.get('http://localhost:3000/users?q=yahoo')
    .then(resp => {
        console.log(resp.data)
    }).catch(error => {
        console.log(error);
    });

The code example searches for the yahoo term.

$ node full_text_search.js 
[ { id: 4,
    first_name: 'Robert',
    last_name: 'Brown',
    email: 'bobbrown432@yahoo.com' },
  { id: '5',
    first_name: 'Roger',
    last_name: 'Bacon',
    email: 'rogerbacon12@yahoo.com' },
  { first_name: 'Fred',
    last_name: 'Blair',
    email: 'freddyb34@yahoo.com',
    id: 6 } ]

The search query returned these three users.

In this tutorial, we have introduced the JSON Server JavaScript library.

List all JavaScript tutorials.