JSON Server Tutorial

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.

Tools

• VSC
• Simple REST ClientVSC extension (Easy to examine your API's responses directly within VSC. Send requests to verify your API)

Or alternatively

• Insomnia

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

constaxios=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

constaxios=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

constaxios=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

constaxios=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

constaxios=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 _orderquery 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

constaxios=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 qparameter.

full_text_search.js

constaxios=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.