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package.json notes

This package is bundled as both a commonjs and es6-compatible NPM bundle. The factor that enables this dual packaging is the "exports" key in the package.json file:

exports

  • require: When this package is in a commonjs environment (e.g. default nodejs) the ./index.js file will be the thing that is 'require'd.
  • import: When this package is in an es6 environment (e.g. bundler, modern nodejs, modern browser) the ./index.mjs will be the thing 'import'ed.

dependencies

  • node-fetch: When the http-client protocol is used, node-fetch supplies 'fetch' for a nodejs client
  • node-web-streams: Although node-fetch is mostly isomorphic, its internal stream is not the same as a web stream reader; we need it to have the same API.
  • spdy: This gives us http2.0 connection multiplexing with a 'natural http module interface'. (http1.1 provides a max of 6 open conns)

Development Notes

For code that is intended to run in all environments (e.g. browser, node) and potentially pass through a bundler step, the following guidelines are helpful:

  • Use single-value module.exports in files, and named exports in wrappers.
  • If using globals, it's also important to use module.exports; for example:
function braid_fetch(...) { ... }

if (typeof module !== 'undefined' && module.exports) {
    module.exports = braid_fetch
}

For a complete list of reasons for the madness, and to learn more about the method we've used to build this package, see https://redfin.engineering/node-modules-at-war-why-commonjs-and-es-modules-cant-get-along-9617135eeca1

Because we require certain libraries that are meant to be used in a nodejs environment only, we also need to provide a hint to bundlers that are targeting a browser environment NOT to load those libraries. This is what the browser field in package.json is for:

  "browser": {
    "node-web-streams": false,
    "node-fetch": false,
    "abort-controller": false
  }

If we don't hint that these libraries should not be loaded in the browser, bundled code that depends on braidjs libraries will fail in the browser.

See also https://github.com/defunctzombie/package-browser-field-spec.