CODEWITHSUNDEEP
node.jsexpressgraphql
Shan-Desai
Shan-Desai

Reputation: 3349

get Index from an Array using Express + GraphQL

I am just getting my hands dirty with GraphQL using Express. I am following the Academind YouTube Series for GraphQL-Express-Node-React. I have just setup a basic GraphQL Schema where I have hardcoded Array of Strings which is returned. I want to create a Query which gives me the index of the element from this hardcoded array using GraphQL (graphiql)

Code

const express = require('express'); // Add Express Module
const bodyParser = require('body-parser'); // Add Body-Parser Middleware for JSON handling in Requests
const graphqlHttp = require('express-graphql'); // Add Middleware for GraphQL Resolvers over Express HTTP
const { buildSchema } = require('graphql'); // Javascript Object-Destructuring (pull objects from packages)

const app = express();

app.use(bodyParser.json()); // JSON parsing Middleware added

app.use('/graphql', graphqlHttp({
    schema: buildSchema(`
        type RootQuery {
            events: [String!]!
            getEventIndex(eventName: String): Int
        }

        type RootMutation {
            createEvent(name: String): String
        }

        schema {
            query: RootQuery
            mutation: RootMutation
        }
    `),
    rootValue: {
        events: () => {
            return ['Cooking', 'All-Night Coding', 'Romantic'];
        },
        getEventIndex: (args) => {
            const _arr = ['Cooking', 'All-Night Coding', 'Romantic'];
            const index = _arr.findIndex(args.eventName);
            return index;
        },
        createEvent: (args) => {
            const eventName = args.name; // same as that of the parameter for `createEvent`
            return eventName;

        }
    },
    graphiql: true
}));

app.listen(3000);

I created a query getEventIndex(eventName: String): Int which takes in the event name and provides me the index (which is integer)

Result in graphiql

query

query {
  getEventIndex(eventName: "Cooking")
}

result

{
  "errors": [
    {
      "message": "Cooking is not a function",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "getEventIndex"
      ]
    }
  ],
  "data": {
    "getEventIndex": null
  }
}

Why would Cooking here be considered as a function and not as an argument in createEvent mutation?

Of course I am jumping into GraphQL without much deep diving into its Specifications but I guess it might be capable of handling parameter based querying too.

Upvotes: 0

Views: 692

Answers (1)

Daniel Rearden
Daniel Rearden

Reputation: 84747

This error is not specific to GraphQL.

Array.findIndex expects a function to be passed in as its first parameter. The function is called for each element in the array until the function returns a truthy value, at which point it returns the index of that element. The value of args.eventName is not a function (it's a String) so you end up with that error.

Either pass it a function, like:

const index = _arr.findIndex(value => value === args.eventName)

or just use Array.indexOf instead, which is probably what you meant to do:

const index = _arr.indexOf(args.eventName)

Upvotes: 1

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