capture.md

capture helper

🔝 REserve documentation

REserve offers a mechanism to capture the response stream and duplicate its content to another writable stream.

function capture (response: ServerResponse, stream: WritableStream): Promise<void>

Types definition for capture

Important

The content is decoded if the content-encoding header contains: gzip, deflate or br (only one, no combination is supported).

Caution

Check the version of Node.js to enable br compression support.

In the following example, three mappings are used :

1. If the request resource exists in the cache folder , it is returned.
2. Otherwise, the second mapping captures and serializes locally the response returned by the last mapping.
3. The last mapping redirects the request to an external site.

mappings: [{
  match: /^\/(.*)/,
  file: './cache/$1'
}, {
  method: 'GET',
  custom: async (request, response) => {
    if (/\.(js|css|svg|jpg)$/.exec(request.url)) {
      const cachePath = join(cacheBasePath, '.' + request.url)
      const cacheFolder = dirname(cachePath)
      await mkdirAsync(cacheFolder, { recursive: true })
      const file = createWriteStream(cachePath) // auto closed
      capture(response, file)
        .catch(reason => {
          console.error(`Unable to cache ${cachePath}`, reason)
        })
    }
  }
}, {
  match: /^\/(.*)/,
  url: 'http://your.website.domain/$1'
}]

Example of capture used to cache resources