Node-js
Node.js Express FrameWork Tutorial - Learn in 10 Minutes
In this tutorial, we will study the Express framework. This framework is built in such a way that...
GraphQL is an application layer server-side technology which is developed by Facebook for executing queries with existing data. GraphQL can optimize RESTful API calls. It gives a declarative way of fetching and updating your data. GraphQL helps you to load data from server to client. It enables programmers to choose the types of requests they like to make.
In this GraphQL tutorial for beginners, you will learn GraphQL basics:
Following are the reasons of using GraphQL:
Here are the important applications of GraphQL:
This GraphQL tutorial is based on Express and NodeJs. Therefore, you can learn GraphQL very easily with a basic understanding of NodeJS.
Now in this GraphQL tutorial, let's learn the key components of GraphQL:
As shown in the above figure, there are three key components of GraphQL: 1) Query, 2) Resolver, and 3) Schema.
The Query is an API request made by the client machine application. It supports augments and points to arrays. Query is used to read or fetch values.
Parts of Query:
Following are the important parts of Query
A field simply indicates that we are asking the server for particular information. Following is a GraphQL example of a field in graphQL query.
query { team { id name } } "data": { "team":[ { "id": 1, "name": "Avengers" } , … ] } }
In the above GraphQL example, we ask the server for the field called team and its subfields like id and name. The GraphQL server returns data in we asked for.
In REST, we can only pass a single set of arguments as URL segments and query parameters. To get a particular profile, a typical REST call will look like the following:
GET /api'team?id=2 Content-Type: application JSON { "id": 2, "name": "Justice League." }
Resolvers provide the directions for converting GraphQL operation into data. They resolve the query to data by defining resolver functions.
It displays the server the process as well as location to fetch data according to a specific field. The resolver also separates database schema and API schema. The separated information helps to modify the content obtained from the database.
A GraphQL schema is the center of GraphQL implementation. It describes the functionality available to the clients which are connecting to it.
Here are important features of GraphQL:
GraphQL client is a code that makes POST requests to a relevant GraphQL Server. You can query a GraphQL API directly, but the good approach is to leverage a dedicated client library using Relay.
This JavaScript library is developed by Facebook for making React applications with GraphQL. GraphQL clients can be a CMS like Drupal, a single page application, a mobile application, etc.
GraphQL servers are servers side implementation of GraphQL's specification. It depicts your data as GraphQL API, which your client program can query for the database.
Gateway is a microservice pattern where you can build a separate service to cope up with other backend services. It offers workable documentation and gives a convenient way to collect data from more than one source with a single request.
A Variable in GraphQL is used to separate the dynamic values from the client query and pass the query as a unique dictionary. Variable in GraphQL can also be used for reusing the query or mutations written by the client with individual arguments. In graphQL, you cannot pass dynamic arguments directly in the query string. The reason is client-side code needs to manipulate query string dynamically at the time when you run the program.
GraphQL has one good way to factorize the dynamic values out of the query. It passes them as a separate dictionary. These values are known as variables. Whenever we working with variables, we need to do the following three things:
Here's what it looks like all together:
query HeroNameAndFriends($episode: Episode) { hero(episode: $episode) { name friends { name } } } { "episode": "JEDI" } { "data": { "hero": { "name": "R2-D2", "friends": [ { "name": "Luke Skywalker" }, { "name": "Han Solo" }, { "name": "Leia Organa" } ] } } }
As you can see in the above GraphQL example, we have simply passed a different variable other than needing to construct a new query.
A mutation is a way to change the dataset in GraphQL. It modifies data in the data store and returns a value. Mutations help you to insert, update, or delete data. Generally, mutations are defined as a schema part.
Here are the important points while designing GraphQL:
Following table shows important difference between GraphQL and REST.
GraphQL | REST |
It follows client-driven architecture. | It follows server-driven architecture. |
GraphQL can be organized in terms of a schema. | REST can be organized in terms of endpoints. |
GraphQL is a growing community. | REST is a very large community. |
The development speed in GraphQL is fast. | The development speed in REST is Slow. |
The learning curve in GraphQL is difficult. | The learning curve in REST is moderate. |
The identity is separated from how you fetch it. | The endpoint you call in REST is the identity of a particular object. |
In GraphQL, the server determines available resources. | The shape and size of the resource is determined by the server in REST. |
GraphQL provides high consistency across all platforms. | It is hard to get consistency across all platforms. |
Here are the GraphQL disadvantages:
The important open source apps and tools used by GraphQL are as follows:
In this tutorial, we will study the Express framework. This framework is built in such a way that...
$20.20 $9.99 for today 4.6 (106 ratings) Key Highlights of Node.js Tutorial PDF 107+ pages eBook...
Bluebird is a fully-featured Promise library for JavaScript. The strongest feature of Bluebird is...
What is Node.js? Node.js is a server-side platform built on Google Chrome's JavaScript Engine. It uses a...
In this tutorial, you will learn Filestream in Node.js Pipes in Node.js Events in Node.js Emitting...
Introduction to Node.js The modern web application has really come a long way over the years with...