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node.jsnode-modulesrequirebuilt-in

How does a NativeModule function and are they cached?

require('http')
console.log(require.cache.http) // undefined

I can't find the http module in require.cache ? How can I detect it was required? I found process.moduleLoadList that contains the string NativeModule http but don't see any reference to the cached module where is it ?

Solution

  • NativeModule means it's not cached: it's compiled. It's defined like this,

    NativeModule: a minimal module system used to load the JavaScript core modules found in lib/**/*.js and deps/**/*.js. All core modules are compiled into the node binary via node_javascript.cc generated by js2c.py, so they can be loaded faster without the cost of I/O. This class makes the lib/internal/*, deps/internal/* modules and internalBinding() available by default to core modules, and lets the core modules require itself via require('internal/bootstrap/loaders') even when this file is not written in CommonJS style.

    Emphasis added around "without the cost of I/O" so no caching needed.

    You can find this system in lib/internal/bootstrap/loaders.js. You can find the mapping of native modules to source code here, but remember they're not read from disk. You can find js2c.py