gulpfile.js

const gulp = require("gulp");
// const debug = require("postcss-debug").createDebugger();

gulp.task("default", ["js", "css"], function() {
    const revReplace = require("gulp-rev-replace");
    const manifest = gulp.src("build/public/rev-manifest.json");

    return gulp
        .src("./src/views/index.pug")
        .pipe(revReplace({ manifest: manifest, replaceInExtensions: [".pug"] }))
        .pipe(gulp.dest("build/views"));
});

gulp.task("css", ["postcss"], function() {
    const rev = require("gulp-rev");

    return gulp
        .src("build/public/css/*.css", { base: "build/public" })
        .pipe(gulp.dest("build/public"))
        .pipe(rev())
        .pipe(gulp.dest("build/public"))
        .pipe(rev.manifest())
        .pipe(gulp.dest("build/public"));
});

gulp.task("js", function() {
    const uglify = require("gulp-uglify");
    return gulp
        .src("src/public/js/*.js")
        .pipe(uglify())
        .pipe(gulp.dest("build/public/js"));
});

gulp.task("postcss", function() {
    const postcss = require("gulp-postcss");
    const plugins = [
        require("postcss-import")(),
        require("postcss-assets")({
            basePath: "src/public/"
        }),
        require("postcss-nested"),
        require("postcss-custom-properties"),
        require("autoprefixer")({ overrideBrowserslist: ["last 2 years"] }),
        require("cssnano")({
            preset: ["default"],
            discardComments: {
                removeAll: true
            }
        })
    ];
    return gulp
        .src("src/public/css/app.css")
        .pipe(postcss(plugins))
        .pipe(gulp.dest("build/public/css"));
});

gulp.task("postcss:dev", function() {
    const postcss = require("gulp-postcss");

    const plugins = [
        require("postcss-import")(),
        require("postcss-assets")({
            basePath: "src/public/"
        }),
        require("postcss-nested"),
        require("postcss-custom-properties")
    ];
    return gulp
        .src("src/public/css/app.css")
        .pipe(postcss(plugins))
        .pipe(gulp.dest("build/public/css"));
});

gulp.task("dev", ["nodemon"], function() {
    const browserSync = require("browser-sync");

    browserSync({
        proxy: "localhost:3000",
        port: 5000,
        open: false,
        notify: true
    });
});

gulp.task("nodemon", function(cb) {
    const nodemon = require("gulp-nodemon");
    const browserSync = require("browser-sync");

    let called = false;
    return nodemon({
            execMap: {
                js: "babel-node"
            },
            watch: ["src/"],
            ext: "js css ico pug",
            script: "src/bootstrap/index.js",
            tasks: ["postcss:dev", "js"]
        })
        .on("start", function() {
            if (!called) {
                called = true;
                cb();
            }
        })
        .on("restart", function() {
            setTimeout(function() {
                browserSync.reload({ stream: false });
            }, 1000);
        });
});