Basic task runner - replace gulp with CLI

task-runner.es6.js

/**
  Beginnings of ES6 node Task runner to replace gulp.
  This example uses PostCSS and Pug to process CSS and HTML templates.
*/

// Global dependencies
const fs = require('fs-extra');
const bs = require('browser-sync').create();
const glob = require('glob');

// Local dependencies
const pug = require('pug');
const postCss = require('postcss');
const postCssPlugins = ["precss","postcss-cssnext","postcss-utilities"].map(require); 

const generators = {
    html: {
        src: 'src/*.pug',
        make: function(inpath) {
            // Set output file path
            var outpath = inpath.replace('src','dist').replace('pug','html');
            // Save file
            fs.outputFile(outpath, pug.renderFile(inpath));
            // Reload page
            bs.reload();
        }
    },
    styles: {
        src: 'src/styles/**/*.postcss',
        make: function(inpath) {
            var outpath = inpath.replace('src','dist').replace('postcss','css');
            postCss(postCssPlugins)
            .process(fs.readFile(inpath), { from: inpath, to: outpath })
            .then(function(result) {
                // Save file
                fs.outputFile(outpath, result.css);
                // Write sourcemaps
                if ( result.map ) fs.outputFile(outpath + '.map', result.map);
                // Reload CSS in browser
                bs.reload(outpath.split('/').pop());
            });
        }
    }
}

const tasks = {
    build: function(){
        for (let gen in generators) {
            log('build:' + gen);
            glob(generators[gen].src).forEach((f) => generators[gen].make(f));
        }
    },
    watch: function() {
        let watched = ['styles'];
        log('test');
        for (let gen in watched) {
            gen = watched[gen];
            bs.watch(generators[gen].src).on('change', generators[gen].make);
        }
        tasks.serve();
    },
    serve: function() {
        log('serve');
        bs.init({
            server: "./dist"
        });
    }
}

function log(task, text) {
    text = text || '';
    console.log(`[${task}] ${text}`)
}

// series task runner
process.argv.splice(2).forEach((taskName) => { 
    if (tasks[taskName]) { 
        log(taskName, 'Started...'); 
        tasks[taskName]();
    } 
});