Parallel Webpack Build

.babelrc

{
    "presets": [ "env", "stage-1" ]
}

build.js

import chalk from "chalk";
import path from "path";
import getopt from "node-getopt";
import { exec } from "child_process";
import webpack from "webpack";
import config from "./webpack.config.prod";

const args = getopt.create([
        [ "", "procid=ARG", "Proc ID for parallel builds" ],
        [ "", "help",  "display this help" ]
    ])
    .bindHelp()
    .parseSystem();

let procid = args.options.procid;

const MAX_PROC = 4;

const entryPoints = config.entry;
const bundleNames = Object.keys(entryPoints);
const QUEUE_SIZE = Math.ceil(bundleNames.length / MAX_PROC);


if(!procid || isNaN(parseInt(procid))) {
    console.log(chalk.cyan("Starting parallel webpack build ..."));
    let children = 0;
    for(let i=0; i<bundleNames.length; i+=QUEUE_SIZE) {
        const cmd = `node_modules/.bin/babel-node build.js --procid=${i}`;
        const child = exec(cmd, (error, stdout, stderr) => {
            if (error) {
                console.error(`${error}`);
                return;
            }
            console.log(`${stdout}`);
            console.log(`${stderr}`);
        });
        ++children;
        child.on("close", () => {
            --children;
            if(children==0) {
                console.log(chalk.cyan("All builds completed"));
                console.log(chalk.green("Static file bundles generated"));
            }
        });
    }
} else {
    procid = parseInt(procid);
    config.entry = bundleNames.slice(procid, procid + QUEUE_SIZE).reduce((acc, cur) => {
        return {
            ...acc,
            [cur]: config.entry[cur]
        };
    }, {})
    webpack(config).run((error, stats) => {
        if(error) {
            console.error(chalk.red(error));
            return 1;
        }

        const jsonStats = stats.toJson();
        const stringStats = stats.toString(config.stats);

        if (jsonStats.hasErrors) {
            return jsonStats.errors.map(error => console.log(chalk.red(error)));
        }
        if (jsonStats.hasWarnings) {
            console.log(chalk.yellow("Webpack generated the following warnings: "));
            jsonStats.warnings.map(warning => console.log(chalkWachalk.yellowrning(warning)));
        }
        console.log(stringStats);
    });
}

package.json

{
    "scripts": {
    "build": "babel-node build.js",
    },
    "author": "Subir",
    "license": "MIT",
    "devDependencies": {
        "babel-cli": "^6.7.7",
        "babel-core": "6.26.0",
        "babel-preset-env": "1.6.0",
        "babel-preset-stage-1": "6.24.1",
        "chalk": "^1.1.3",
        "node-getopt": "^0.2.3",
        "webpack": "3.6.0"
    }
}

webpack.config.prod.js

import webpack from "webpack";
import glob from "glob";

const INIT_DIR = path.join(__dirname, "src", "init");
const OUT_DIR = path.join(__dirname, "dist");

const entryPoints = glob.sync(path.join(INIT_DIR, "*.js"))
    .reduce((obj, filePath) => {
        const pieces = path.parse(filePath);
        return {
            ...obj,
            [pieces.name]: path.join(INIT_DIR, pieces.name)
        };
    }, {});

export default {
    entry: entryPoints,
    output: {
        path : OUT_DIR,
        filename: "[name].min.js"
    }    
};