const { loading, error, data } = useQuery(GET_DOGS, {
  fetchPolicy: "no-cache"});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> loading<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

function App() {
  const { data } = useQuery(IS_LOGGED_IN);
  return data.isLoggedIn ? <Pages /> : <Login />;
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">function</span> <span class="token function">App</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token constant">JSX</span><span class="token punctuation">.</span>Element</code></pre>

const GET_DOG = gql`
  query GetDog($dogId: ID!) {
    dog(id: $dogId) {
      name
      breed
    }
  }
`;

function Dog({ id }) {
  const { loading, error, data } = useQuery(GET_DOG, {    variables: {      dogId: id    },  });  // ...render component...
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> <span class="token constant">GET_DOG</span><span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

function ExchangeRates() {
  const { loading, error, data } = useQuery(EXCHANGE_RATES);
  if (loading) return <p>Loading...</p>;
  if (error) return <p>Error :(</p>;

  return data.rates.map(({ currency, rate }) => (
    <div key={currency}>
      <p>
        {currency}: {rate}
      </p>
    </div>
  ));
}
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">function</span> <span class="token function">ExchangeRates</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

import React from "react";
import { ApolloConsumer, useApolloClient, useQuery, gql } from "@apollo/client";

const GET_MESSAGE_COUNT = gql`
  query GetMessageCount {
    messageCount @client {
      total
    }
  }
`;

const resolvers = {
  Query: {
    messageCount: (_, args, { cache }) => {
      // ... calculate and return the number of messages in
      // the cache ...
      return {
        total: 123,
        __typename: "MessageCount",
      };
    },
  },
};

export function MessageCount() {
  const client = useApolloClient();
  client.addResolvers(resolvers);

  const { loading, data: { messageCount } } = useQuery(GET_MESSAGE_COUNT);

  if (loading) return "Loading ...";

  return (
    <p>
      Total number of messages: {messageCount.total}
    </p>
  );
};
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">namespace</span> React
<span class="token keyword">import</span> React</code></pre>

import { ApolloClient, InMemoryCache } from "@apollo/client";

const client = new ApolloClient({
  cache: new InMemoryCache(),
  uri: "/graphql"
});

client.query({
  query: MY_QUERY,
  context: {
    // example of setting the headers with context per operation
    headers: {
      special: "Special header value"
    }
  }
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">class</span> <span class="token class-name">ApolloClient<span class="token operator">&lt;</span>TCacheShape<span class="token operator">></span></span>
<span class="token keyword">import</span> ApolloClient</code></pre>

// Invoke the query and log the person's name
client.query({ query }).then(response => {
  console.log(response.data.name);
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

// const client = ...

client
  .query({
    query: gql`
      query GetRates {
        rates(currency: "USD") {
          currency
        }
      }
    `
  })
  .then(result => console.log(result));
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

// Query that fetches all existing to-do items
const query = gql`
  query MyTodoAppQuery {
    todos {
      id
      text
      completed
    }
  }
`;

// Get the current to-do list
const data = client.readQuery({ query });

// Create a new to-do item
const myNewTodo = {
  id: '6',
  text: 'Start using Apollo Client.',
  completed: false,
  __typename: 'Todo',
};

// Write back to the to-do list, appending the new item
client.writeQuery({
  query,
  data: {
    todos: [...data.todos, myNewTodo],
  },
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> query<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

import React from "react";
import { ApolloConsumer, useApolloClient, useQuery, gql } from "@apollo/client";

const GET_MESSAGE_COUNT = gql`
  query GetMessageCount {
    messageCount @client {
      total
    }
  }
`;

const resolvers = {
  Query: {
    messageCount: (_, args, { cache }) => {
      // ... calculate and return the number of messages in
      // the cache ...
      return {
        total: 123,
        __typename: "MessageCount",
      };
    },
  },
};

export function MessageCount() {
  const client = useApolloClient();
  client.addResolvers(resolvers);

  const { loading, data: { messageCount } } = useQuery(GET_MESSAGE_COUNT);

  if (loading) return "Loading ...";

  return (
    <p>
      Total number of messages: {messageCount.total}
    </p>
  );
};
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token punctuation">(</span>alias<span class="token punctuation">)</span> <span class="token keyword">namespace</span> React
<span class="token keyword">import</span> React</code></pre>

client.writeQuery({
  query: gql`
    query WriteTodo($id: Int!) {
      todo(id: $id) {
        id
        text
        completed
      }
    }`,
  data: { // Contains the data to write
    todo: {
      __typename: 'Todo',
      id: 5,
      text: 'Buy grapes 🍇',
      completed: false
    },
  },
  variables: {
    id: 5
  }
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

  client.writeQuery({
    query: gql`
      query GetCartItems {
        cartItems
      }
    `,
    data: {
      cartItems: []
    }
  });
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

client.writeQuery({
  query: gql`
    query Feed($type: FeedType!) {
      feed(type: $type) @connection(key: "feed", filter: ["type"]) {
        id
      }
    }
  `,
  variables: {
    type: "top",
  },
  data: {
    feed: [],
  },
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> client<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>

// Query that fetches all existing to-do items
const query = gql`
  query MyTodoAppQuery {
    todos {
      id
      text
      completed
    }
  }
`;

// Get the current to-do list
const data = client.readQuery({ query });

// Create a new to-do item
const myNewTodo = {
  id: '6',
  text: 'Start using Apollo Client.',
  completed: false,
  __typename: 'Todo',
};

// Write back to the to-do list, appending the new item
client.writeQuery({
  query,
  data: {
    todos: [...data.todos, myNewTodo],
  },
});
<pre class="typing-tooltip"><code data-language="javascript" class="language-javascript"><span class="token keyword">const</span> query<span class="token operator">:</span> <span class="token builtin">any</span></code></pre>