How to build a Graqhql mutation with existing variables - node.js

Question

This might seem like an odd question, or something really straightforward, but honestly I am struggling to figure out how to do this. I am working in Node.js and I want to set data I have saved on a node object into my GraphQL mutation.
I'm working with a vendor's GraqhQL API, so this isn't something I have created myself, nor do I have a schema file for it. I'm building a mutation that will insert a record into their application, and I can write out everything manually and use a tool like Postman to manually create a new record...the structure of the mutation is not my problem.
What I'm struggling to figure out is how to build the mutation with variables from my node object without just catting a bunch of strings together.
For example, this is what I'm trying to avoid:
class MyClass {
constructor() {
this.username = "my_username"
this.title = "Some Title"
}
}
const obj = new MyClass()
let query = "mutation {
createEntry( input: {
author: { username: \"" + obj.username + "\" }
title: \"" + obj.title + "\"
})
}"
I've noticed that there are a number of different node packages out there for working with Graphql, but none of their documentation that I've seen really addresses the above situation. I've been completely unsuccessful in my Googling attempts, can someone please point me in the right direction? Is there a package out there that's useful for just building queries without requiring a schema or trying to send them at the same time?

Answer 1

GraphQL services typically implement this spec when using HTTP as a transport. That means you can construct a POST request with four parameters:
query - A Document containing GraphQL Operations and Fragments to execute.
operationName - (Optional): The name of the Operation in the Document to execute.
variables - (Optional): Values for any Variables defined by the Operation.
extensions - (Optional): This entry is reserved for implementors to extend the protocol however they see fit.
You can use a Node-friendly version of fetch like cross-fetch, axios, request or any other library of your choice to make the actual HTTP request.
If you have dynamic values you want to substitute inside the query, you should utilize variables to do so. Variables are defined as part of your operation definition at the top of the document:
const query = `
mutation ($input: SomeInputObjectType!) {
createEntry(input: $input) {
# whatever other fields assuming the createEntry
# returns an object and not a scalar
}
}
`
Note that the type you use will depend on the type specified by the input argument -- replace SomeInputObjectType with the appropriate type name. If the vendor did not provide adequate documentation for their service, you should at least have access to a GraphiQL or GraphQL Playground instance where you can look up the argument's type. Otherwise, you can use any generic GraphQL client like Altair and view the schema that way.
Once you've constructed your query, make the request like this:
const variables = {
input: {
title: obj.title,
...
}
}
const response = await fetch(YOUR_GRAPHQL_ENDPOINT, {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ query, variables }),
})
const { data, errors } = await response.json()