求Firefox插件实现：拦截POST请求修改参数后放行

Alright, let's tackle this problem head-on—you want to regain control over how many comments you see per page on example.org, right? The good news is building a Firefox extension to intercept and modify that POST request is totally doable. Here's a complete, step-by-step solution tailored to your scenario:

First, create a new folder for your extension (name it something like comment-pagination-fixer). Inside it, you'll need two core files:

• manifest.json (tells Firefox what your extension does and what permissions it needs)
• background.js (handles the actual request interception and modification)

We'll use Firefox's WebExtensions API with manifest version 3 (the latest standard for better security and performance). Paste this into manifest.json:

{
  "manifest_version": 3,
  "name": "Comment Pagination Fixer",
  "version": "1.0",
  "description": "Restores custom comment pagination on example.org",
  "permissions": ["webRequest", "webRequestBlocking", "https://example.org/*"],
  "background": {
    "scripts": ["background.js"]
  }
}

• The webRequest and webRequestBlocking permissions let us intercept and alter requests before they're sent.
• We restrict access only to example.org to follow security best practices (no unnecessary broad permissions).

This is where the magic happens. The script listens for POST requests to the comments API, parses the JSON body, updates the pagination parameter, and sends the modified request. Paste this into background.js:

// Listen for POST requests to the specific comments API endpoint
browser.webRequest.onBeforeRequest.addListener(
  (details) => {
    // Skip requests without a readable JSON body
    if (!details.requestBody || !details.requestBody.raw) return;

    // Convert the raw byte body to a readable string, then parse the JSON
    const decoder = new TextDecoder("utf-8");
    const rawBody = details.requestBody.raw[0].bytes;
    const requestData = JSON.parse(decoder.decode(rawBody));

    // Modify the pagination parameter (replace "perPage" with the actual key from the API's JSON)
    // Set this to your desired number of comments per page (e.g., 100, 500)
    requestData.perPage = 100;

    // Convert the modified JSON back to raw bytes for the request
    const encoder = new TextEncoder();
    const modifiedBody = encoder.encode(JSON.stringify(requestData));

    // Return the modified request to send to the server
    return {
      requestBody: {
        raw: [{ bytes: modifiedBody }]
      }
    };
  },
  // Target the exact API endpoint you identified
  { urls: ["https://example.org/api.html?GET_COMMENTS"] },
  // Required permissions to access and modify the request body
  ["blocking", "requestBody"]
);

• Critical Note: Replace "perPage" with the actual property name in the POST JSON body that controls comment count per page (use the key you found in your research).
• Adjust the value 100 to whatever number you prefer (500, 200, etc.—match the old options the site used).

1. Open Firefox and navigate to about:debugging
2. Click "This Firefox" in the left sidebar
3. Click "Load Temporary Add-on..."
4. Navigate to your extension folder and select the manifest.json file

That's it! Now when you load comments on example.org, the extension will automatically tweak the POST request to use your desired comment count per page.

• If the extension isn't working, open the background script console: in about:debugging, click "Inspect" next to your extension to view logs. Look for errors like incorrect JSON parsing or a mismatched API endpoint.
• If example.org updates their API path or parameter names, you'll need to adjust the urls match pattern and the parameter key in background.js.
• For older Firefox versions (pre-109), switch to manifest version 2 by updating the manifest_version to 2 and keeping the background field as is—version 2 is still supported for legacy setups.

内容的提问来源于stack exchange，提问作者jo1storm