gulpfile.js

const fs = require("fs");
const gulp = require("gulp");
const plug = require("gulp-load-plugins")({
    rename: {
        "gulp-clean-css": "uglifycss",
        "gulp-uglify": "uglifyjs",
        "gulp-html-minifier2": "html",
    },
});

//<editor-fold desc="IDE help only">
// noinspection PointlessBooleanExpressionJS, ConstantIfStatementJS just here for ide inspection help
if (false) {
    // noinspection UnreachableCodeJS just here for ide inspection help
    plug.concat = require("gulp-concat");
    plug.html = require("gulp-html-minifier2");
    plug.ignore = require("gulp-ignore");
    plug.less = require("gulp-less");
    plug.rename = require("gulp-rename");
    plug.replace = require("gulp-replace");
    plug.sourcemaps = require("gulp-sourcemaps");
    plug.typescript = require("gulp-typescript");
    plug.uglifycss = require("gulp-clean-css");
    plug.uglifyjs = require("gulp-uglify");
}
//</editor-fold>

//<editor-fold desc="Task Less/CSS">
const css_task = () => gulp
    .src("src/less/*.less")
    .pipe(plug.sourcemaps.init())

    .pipe(plug.less())
    .pipe(plug.concat("style.min.css"))
    .pipe(plug.uglifycss({level: 2}))
    .pipe(plug.sourcemaps.write("./", {includeContent: false, sourceRoot: "src/less/"}))
    .pipe(gulp.dest("build/"));
gulp.task("css", css_task);
//</editor-fold>

//<editor-fold desc="Task Typescript">
const ts_task = () => gulp
    .src(["src/ts/*.ts", "!ts/*.d.ts"])
    .pipe(plug.sourcemaps.init())
    .pipe(plug.typescript({"target": "ES5"})) // uglifyjs dosn't work with ES6
    .pipe(plug.concat("app.min.js"))
    .pipe(plug.uglifyjs())
    .pipe(plug.sourcemaps.write("./", {includeContent: false, sourceRoot: "src/ts/"}))
    .pipe(gulp.dest("build/"));
gulp.task("ts", ts_task);
//</editor-fold>

//<editor-fold desc="Task HTML">
const html_task = () => gulp
    .src("src/html/index.html")
    .pipe(plug.html(
        {
            collapseBooleanAttributes: true,
            collapseWhitespace: true,
            decodeEntities: true,
            removeAttributeQuotes: true,
            removeComments: true,
            removeEmptyAttributes: true,
            removeOptionalTags: true,
            removeRedundantAttributes: true,
            removeScriptTypeAttributes: true,
            removeStyleLinkTypeAttributes: true,
            sortAttributes: true,
            sortClassName: true,
            useShortDoctype: true,
        }))
    .pipe(plug.replace(
        "<link href=style.min.css rel=stylesheet>",
        "<style>" +
        fs.readFileSync("build/style.min.css", "utf8")
            .replace("/*# sourceMappingURL=style.min.css.map */", "")
            .trim() +
        "</style>",
    ))
    .pipe(plug.replace(
        "<script defer src=app.min.js>",
        "<script defer>" +
        fs.readFileSync("build/app.min.js", "utf8")
            .replace("//# sourceMappingURL=app.min.js.map", "")
            .trim() +
        "</script>",
    ))
   .pipe(gulp.dest("build/"));
gulp.task("html", html_task);
//</editor-fold>

gulp.task("default", gulp.series([gulp.parallel("css", "ts"), "html"]));