webpack.js

const webpack = require('webpack');
const path = require('path');

const mode = process.argv[2];
let config = require(path.resolve(process.argv[3] || 'webpack.config'));
if(typeof config === 'function') config = config(mode);
config = Array.isArray(config) ? config : [config];
for(const item of config) item.mode = mode  === 'watch' ? 'development' : mode;

let lastHash = null;
function compilerCallback(err, stats) {
    if(mode !== 'watch' || err) compiler.purgeInputFileSystem();
    if(err) {
        lastHash = null;
        console.error(err.stack || err);
        if(err.details) console.error(err.details);
        process.exit(1);
    }
    if(stats.hash !== lastHash) {
        lastHash = stats.hash;
        const statsString = stats.toString({colors: require("supports-color"), context: config[0].context, cached: false, cachedAssets: false, exclude: ['node_modules']});
        if(statsString) process.stdout.write(statsString + '\n');
    }

    if(mode !== 'watch' && stats.hasErrors()) {
        process.exitCode = 2;
        console.error('FULL ERROR', stats.stats[0].compilation.errors[0]);
    }
}

console.log(config);

const compiler = webpack(config);
if(mode === 'watch') compiler.watch({}, compilerCallback);
else compiler.run(compilerCallback);