如何将GraphQL查询中的变量与值进行比较

query GetUser($filter: String!) {
  user(filter: $filter) {
    id
    name
  }
}

const axios = require('axios');

const query = `
  query GetUser($filter: String!) {
    user(filter: $filter) {
      id
      name
    }
  }
`;

const variables = {
  filter: "example"
};

axios.post('https://api.example.com/graphql', {
  query,
  variables
})
  .then(response => {
    console.log(response.data);
  })
  .catch(error => {
    console.error(error);
  });

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

const schema = buildSchema(`
  type Query {
    user(filter: String!): User
  }

  type User {
    id: ID
    name: String
  }
`);

const root = {
  user: ({ filter }) => {
    if (filter === "example") {
      return {
        id: 1,
        name: "John Doe"
      };
    } else {
      return null;
    }
  }
};

const app = express();

app.use('/graphql', graphqlHTTP({
  schema,
  rootValue: root,
  graphiql: true
}));

app.listen(3000, () => {
  console.log('GraphQL server is running on http://localhost:3000/graphql');
});