Simple sample of gulpjs file. Tasks of this gulpfile is: combine js file together, run babel to convert ES6 to lower compatible version, remove debugging commands like console.log, minify, store in two place.

gulpfile.js

const gulp = require('gulp');
const concat = require('gulp-concat');
const rename = require('gulp-rename');
const uglify = require('gulp-uglify');
const stripDebug = require('gulp-config-strip-debug');
const minifyCSS = require('gulp-minify-css');
const babel = require('gulp-babel');
const include = require("gulp-include");
const gutil = require('gulp-util');

//Add list of js files here
const jsFiles = [
    'src/js/*.js',
];

//Add list of js files here
const cssFiles = [
  'src/css/*.css'
];

//Destination path
const jsDest = 'dist', cssDest = 'dist', distFileName = 'app', jsDest2 = 'other/dist';

gulp.task('css', function () {
    return gulp.src(cssFiles)
        .pipe(minifyCSS())
        .pipe(concat(distFileName+'.min.css'))
        .pipe(gulp.dest(cssDest));
});


gulp.task('scripts', function () {
    return gulp.src(jsFiles)
        .pipe(babel({presets: ['env']}))
        .pipe(concat(distFileName + '.js'))
        .pipe(gulp.dest(jsDest))
        .pipe(gulp.dest(jsDest2))
        .pipe(uglify().on('error', function (err) {
            gutil.log(gutil.colors.red('[Error]'), err.toString());
            this.emit('end');
        }))
        .pipe(rename(distFileName+'.min.js'))
        .pipe(gulp.dest(jsDest))
        .pipe(gulp.dest(jsDest2));
});

gulp.task('prod', function () {
    return gulp.src(jsFiles)
        .pipe(babel({presets: ['env']}))
        .pipe(stripDebug())
        .pipe(concat(distFileName+'.js'))
        .pipe(gulp.dest(jsDest))
        .pipe(gulp.dest(jsDest2))
        .pipe(uglify().on('error', function (err) {
            gutil.log(gutil.colors.red('[Error]'), err.toString());
            this.emit('end');
        }))
        .pipe(rename(distFileName+'.min.js'))
        .pipe(gulp.dest(jsDest))
        .pipe(gulp.dest(jsDest2));
});

// Rerun the task when a file changes
gulp.task('watch', function () {
    gulp.watch(jsFiles, ['scripts']);
});

// The default task (called when you run `gulp` from cli)
gulp.task('default', ['scripts']);

package.json

{
  "name": "",
  "version": "",
  "description": "",
  "main": "gulpfile.js",
  "dependencies": {
    "webpack": "^3.0.0",
    "jquery": "^3.2.1"
  },
  "devDependencies": {
    "babel-cli": "^6.26.0",
    "babel-plugin-transform-es2015-classes": "^6.24.1",
    "babel-preset-env": "^1.6.0",
    "gulp": "^3.9.1",
    "gulp-babel": "^7.0.0",
    "gulp-bundle-assets": "^2.28.0",
    "gulp-concat": "^2.6.1",
    "gulp-config-strip-debug": "^1.0.0",
    "gulp-rename": "^1.2.2",
    "gulp-uglify": "^3.0.0"
  },
  "scripts": {
    "prod": "./node_modules/.bin/gulp prod",
    "build": "./node_modules/.bin/gulp",
    "watch": "./node_modules/.bin/gulp watch",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": ""
}