SyntaxError: Unexpected identifier in one of your dependencies

[evgenykon]

Problem:

> ./node_modules/webpack/bin/webpack.js --mode=production

/srv/quinto-circle/node_modules/compression-webpack-plugin/node_modules/pkg-dir/index.js:5
const pkgDir = async cwd => {
                     ^^^
SyntaxError: Unexpected identifier
    at NativeCompileCache._moduleCompile (/srv/quinto-circle/node_modules/v8-compile-cache/v8-compile-cache.js:240:18)
    at Module._compile (/srv/quinto-circle/node_modules/v8-compile-cache/v8-compile-cache.js:186:36)
    at Object.Module._extensions..js (module.js:579:10)
...
npm ERR! Linux 4.4.0-75-generic
npm ERR! argv "/home/vagrant/.nvm/versions/node/v6.10.3/bin/node" "/home/vagrant/.nvm/versions/node/v6.10.3/bin/npm" "run" "webpack"
npm ERR! node v6.10.3
npm ERR! npm  v3.10.10

My package.json dependencies

{
  ...
  "dependencies": {
    "chart.js": "^2.8.0",
    "chartjs-plugin-labels": "^1.1.0",
    "jquery": "^3.4.1"
  },
  "devDependencies": {
    "babel-loader": "^7.1.5",
    "compression-webpack-plugin": "^3.0.0",
    "node-sass": "^4.12.0",
    "webpack": "^4.39.3",
    "webpack-cli": "^3.3.7"
  }
}

Looking in plugin dependencies, and found that bugged version of pkg-dir placed in your package dependencies

$cd node_modules/compression-webpack-plugin
$ find . -name "*.json" -type f -exec grep -H '"pkg-dir":' {} \;
./node_modules/find-cache-dir/package.json:    "pkg-dir": "^4.1.0"

[sindresorhus]

This package requires Node.js 8, you're on Node.js 6:

https://github.com/avajs/find-cache-dir/blob/da06f099b74b7b7e836317ea80794700bdb32fad/package.json#L8