> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crawlspace.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Sample code

> Spark inspiration for your next web crawling project

What can you build with a web crawler?
Read the following examples to get an idea of the types of data you can collect on Crawlspace.
Copy/paste these examples into your crawler's `main.ts` file to try them out for yourself.
Don't forget to adjust your crawler's [configuration settings](/build/configuration).

### Find prospective customers

In this example, we find companies on Vercel who use Google Tag Manager.

```ts theme={"system"}
export default {
  init() {
    return ["https://news.ycombinator.com"];
  },
  schema({ z }) {
    // columns are defined as Zod types
    return z.object({
      title: z.string(),
      description: z.string(),
      is_vercel: z.boolean(),
      has_gtm: z.boolean(),
      // describing a field as unique allows \`onConflict\` to upsert
      url: z.string().describe("unique"),
    });
  },
  onResponse({ $, $$, enqueue, response }) {
    const isVercel = response.headers.get('server') === 'Vercel';
    const domain = "googletagmanager.com";
    const usesGTM = !!$(\`link[href*="\${domain}"],iframe[src*="\${domain}"]\`);
    // get the URL of every link on the page to continue traversal
    enqueue($$("a[href]"));
    // upsert into sqlite db if both conditions are true
    if (isVercel && usesGTM) {
      const title = $("head > title")?.innerText;
      const description = $("meta[name='description']")?.getAttribute("content");
      const row = { title, description, is_vercel: isVercel, has_gtm: usesGTM };
      return {
        upsert: { row, onConflict: "url" }
      };
    }
  }
} as Crawler;
```

### RAG your docs

You can crawl your own documentation websites to chat with your docs using retrieval-augmented generation (RAG).
Scrape content on a scheduled interval and store embeddings of each page's markdown.

```ts theme={"system"}
export default {
  init() {
    return ["https://docs.example.com"];
  },
  schema({ z }) {
    return z.object({
      title: z.string(),
      description: z.string(),
      // describing a field as unique allows \`onConflict\` to upsert
      url: z.string().describe("unique"),
    });
  },
  async onResponse({ $, $$, enqueue, ai, getMarkdown }) {
    // scrape page details with query selectors
    const row = {
      title: $("head > title")?.innerText,
      description: $("meta[name='description']")?.getAttribute("content"),
    };
    // convenience methods to generate, chunk, and embed markdown
    const markdown = getMarkdown($("body"));
    const { embeddings } = await ai.embed(markdown, { dimensions: 768 });
    // get the URL of every link on the page to continue traversal
    enqueue($$("a[href]"));
    return {
      upsert: { row, onConflict: "url", embeddings },
      attach: { content: markdown },
    };
  }
} as Crawler;
```

### Conduct market research

In this example, we extract pricing data from all SaaS marketing sites that we can find.

```ts theme={"system"}
export default {
  init() {
    // start the crawl on Hacker News
    return ["https://news.ycombinator.com"];
  },
  schema({ z }) {
    return z.object({
      tiers: z.array(
        z.object({
          planName: z.string(),
          monthlyPrice: z.union([z.number().int(), z.string()]),
        }),
      ),
    });
  },
  async onResponse({ $, $$, ai, enqueue, response, z }) {
    // enqueue the homepage of each link on the current page
    const rootPages = $$("a[href]").map((a) => new URL(a.href).origin);
    enqueue(rootPages);
    // conditionally run inference
    const isPricingPage = response.url.endsWith("/pricing");
    if (isPricingPage) {
      const row = await ai.extract($("body"), {
        model: "meta/llama-3.3-70b",
        instruction: "Find the pricing plan of each tier",
        schema: setup.schema({ x }),
      });
      return {
        upsert: { row, onConflict: "url" },
      };
    }
  }
} as Crawler;
```

### Monitor community growth

Track Discord server popularity as a leading indicator of virality.

```ts theme={"system"}
export default {
  init() {
    // start the crawl on Hacker News
    return ["https://news.ycombinator.com"];
  },
  schema({ z }) {
    return z.object({
      server_name: z.string(),
      num_members: z.number().int(),
      // \`url\` and \`created_at\` are automatically provided
    });
  },
  async onResponse({ $, $$, enqueue, ai, response, z }) {
    // enqueue the home page of each link, and any discord invite links
    const allUrls = $$("a[href]").map((a) => new URL(a.href).origin);
    const discordUrls = $$("a[href*='discord.com/invite/']");
    enqueue([...discordUrls, ...allUrls]);
    // if the current page is the "join discord community" page
    if (response.url.startsWith('https://discord.com/invite/')) {
      // extract data that conforms to your schema (or any Zod object)
      const schema = setup.schema({ z });
      const row = await ai.extract<z.infer<typeof schema>>($("html"), {
        model: "meta/llama-3.1-8b",
        instruction: "Find the server name and number of members",
        schema,
      });
      return {
        insert: { row },
      };
    }
  }
} as Crawler;
```

### Start a database of images

Build your own image search engine, using custom logic that you define.

```ts theme={"system"}
export default {
  init() {
    // return an array of URLs to start the crawl
    return ["https://news.ycombinator.com"];
  },
  schema({ z }) {
    // columns are defined as Zod types
    return z.object({
      content_type: z.string(),
      alt_text: z.string(),
      // describing a field as unique allows \`onConflict\` to upsert
      url: z.string().describe("unique"),
    });
  },
  async onResponse({ $, $$, enqueue, metadata, response }) {
    const images = $$('img[alt][src]').map(image => ({
      url: image.src,
      // include arbitrary metadata alongside the enqueued request...
      metadata: { alt_text: image.getAttribute('alt') },
    }));
    const links = $$('a');
    enqueue([...images, ...links]);
    const contentType = response.headers.get('content-type');
    if (contentType?.startsWith('image/')) {
      // ...to access later in the response
      const row = { content_type: contentType, ...metadata };
      return {
        upsert: { row, onConflict: "url" },
        attach: { content: (await response.blob()), metadata },
      };
    }
  }
} as Crawler;
```