Express and GraphQL API Passing Arguments

client.js

var dice = 3;
var sides = 6;
var query = `query RollDice($dice: Int!, $sides: Int) {
  rollDice(numDice: $dice, numSides: $sides)
}`;

fetch('/graphql', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Accept': 'application/json',
  },
  body: JSON.stringify({
    query,
    variables: { dice, sides },
  })
})
  .then(r => r.json())
  .then(data => console.log('data returned:', data));

Passing-Arguments.md

Passing Arguments

Just like a REST API, it's common to pass arguments to an endpoint in a GraphQL API. By defining the arguments in the schema language, typechecking happens automatically. Each argument must be named and have a type. For example, in the Basic Types documentation we had an endpoint called rollThreeDice:

https://graphql.org/graphql-js/passing-arguments/

server.js

var express = require('express');
var { graphqlHTTP } = require('express-graphql');
var { buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
  type Query {
    rollDice(numDice: Int!, numSides: Int): [Int]
  }
`);

// The root provides a resolver function for each API endpoint
var root = {
  rollDice: ({numDice, numSides}) => {
    var output = [];
    for (var i = 0; i < numDice; i++) {
      output.push(1 + Math.floor(Math.random() * (numSides || 6)));
    }
    return output;
  }
};

var app = express();
app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true,
}));
app.listen(4000);
console.log('Running a GraphQL API server at localhost:4000/graphql');