Webpack – Get compilation source

getCompilationSource.ts

import { createFsFromVolume, Volume } from 'memfs'

const fs = createFsFromVolume(new Volume())
const compiler = webpack({
  entry: 'file.js',
  output: { filename: 'main.js' }
})

// Compile the file to memory.
compiler.outputFileSystem = fs

await new Promise((resolve, reject) => compiler.run((error) => {
  if (error) reject(error)
  resolve()
})

// Read the compiled file from memory. 
const source = memoryFs.readFileSync('dist/main.js', 'utf8').toString()