Fetch introspectionQuery from your graphQL api and create `graphql.schema.json` file. Works with local host with https(self-signed certificate)

introspectionQuery.js

const fetch = require('isomorphic-unfetch')
const fs = require('fs')
const path = require('path')
const https = require('https')

// by-pass self-signed certificate rejection on local server
const agent = new https.Agent({
  rejectUnauthorized: false,
})

// CHANGE THIS TO YOUR API URL
const URL_API_ENDPOINT = ''
const writeFileDestination = path.resolve(__dirname, './graphql.schema.json')

fetch(URL_API_ENDPOINT, {
  agent,
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    operationName: 'IntrospectionQuery',
    variables: {},
    query: `
      query IntrospectionQuery {
        __schema {
          queryType {
            name
          }
          mutationType {
            name
          }
          subscriptionType {
            name
          }
          types {
            ...FullType
          }
          directives {
            name
            description
            locations
            args {
              ...InputValue
            }
          }
        }
      }

      fragment FullType on __Type {
        kind
        name
        description
        fields(includeDeprecated: true) {
          name
          description
          args {
            ...InputValue
          }
          type {
            ...TypeRef
          }
          isDeprecated
          deprecationReason
        }
        inputFields {
          ...InputValue
        }
        interfaces {
          ...TypeRef
        }
        enumValues(includeDeprecated: true) {
          name
          description
          isDeprecated
          deprecationReason
        }
        possibleTypes {
          ...TypeRef
        }
      }

      fragment InputValue on __InputValue {
        name
        description
        type {
          ...TypeRef
        }
        defaultValue
      }

      fragment TypeRef on __Type {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
                ofType {
                  kind
                  name
                  ofType {
                    kind
                    name
                    ofType {
                      kind
                      name
                    }
                  }
                }
              }
            }
          }
        }
      }
    `,
  }),
})
  .then(result => result.json())
  .then(result => {
    fs.writeFile(writeFileDestination, JSON.stringify(result), err => {
      if (err) {
        console.error('Error writing fragmentTypes file', err)
      } else {
        console.log('GraphQL schemas successfully extracted!')
      }
    })
  })