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how to combine all yarn files with gulp

I have yarn up and running, have figured out a bit how it works, and made my inroads into figuring out gulp, after having discovered how to install version 4 instead of the default version that throws deprecation errors.
Now I have installed 3 packages with yarn, and it has downloaded a LOT of dependencies. No problem, one can use a gulp file to combine those into one javascript(or so i'm told)
The only thing is, how do I do that whilst maintaining the yarn dependencies as yarn builds those up? How would I format my gulp task for combining the yarn libaries i've added?
My gulp task currently looks like this:
//Concatenate & Minify JS
gulp.task('scripts', function() {
return gulp.src('assets/javascript/*.js')
.pipe(concat('all.js'))
.pipe(gulp.dest('assets/dist'))
.pipe(rename('all.min.js'))
.pipe(uglify())
.pipe(gulp.dest('assets/dist/js'));
});
And this concatenates my scripts as it should, but when I wanted to add the yarn folder it hit me that yarn manages dependencies and what not so everything has it's correct dependency and such. I doubt I can just add them all to the same file and hope all is well.(or can I?)
I run this task with yarn run watch
I've added the following packages: html5shiv, jquery, modernizr
What would be the correct way to add the yarn files in in assets/node_modules?

After long searching I found https://pawelgrzybek.com/using-webpack-with-gulpjs/
which gave me the following solution:
Execute the command:
sudo yarn add global gulp webpack webpack-stream babel-core babel-loader babel-preset-latest
create a webpack.config.js file
enter in it:
module.exports = {
output: {
filename: 'bundle.js', // or whatever you want the filename to be
},
module: {
rules: [
{
test: /\.(js|jsx)$/,
exclude: /(node_modules)/,
loader: 'babel-loader',
query: {
presets: [
['latest', { modules: false }],
],
},
},
],
},
};
Then create a gulpfile.js
var gulp = require('gulp');
var webpack = require('webpack');
var webpackStream = require('webpack-stream');
var webpackConfig = require('./webpack.config.js');
gulp.task('watch', watchTask);
gulp.task('default', defaultTask);
gulp.task('scripts', function() {
return gulp.src('assets/javascript/*.js')
.pipe(webpackStream(webpackConfig), webpack)
.pipe(gulp.dest('./assets/js')); // Or whereever you want your js file to end up.
});
function watchTask(done) {
// Wherever you stored your javascript files
gulp.watch('assets/javascript/*.js', gulp.parallel('scripts'))
done();
}
function defaultTask(done) {
// place code for your default task here
done();
}
Then in the directory execute yarn watch and have it run in the background where you can throw an eye on it now and then.

How to minify ES6 functions with gulp-uglify?

When I run gulp I get the following error:
[12:54:14] { [GulpUglifyError: unable to minify JavaScript]
cause:
{ [SyntaxError: Unexpected token: operator (>)]
message: 'Unexpected token: operator (>)',
filename: 'bundle.js',
line: 3284,
col: 46,
pos: 126739 },
plugin: 'gulp-uglify',
fileName: 'C:\\servers\\vagrant\\workspace\\awesome\\web\\tool\\bundle.js',
showStack: false }
The offending line contains an arrow function:
let zeroCount = numberArray.filter(v => v === 0).length
I know I can replace it with the following to remedy the minification error by abandoning ES6 syntax:
let zeroCount = numberArray.filter(function(v) {return v === 0;}).length
How can I minify code containing ES6 features via gulp?

You can leverage gulp-babel as such...
const gulp = require('gulp');
const babel = require('gulp-babel');
const uglify = require('gulp-uglify');
gulp.task('minify', () => {
return gulp.src('src/**/*.js')
.pipe(babel({
presets: ['es2015']
}))
.pipe(uglify())
// [...]
});
This will transpile your es6 early in the pipeline and churn out as widely supported "plain" javascript by the time you minify.
May be important to note - as pointed out in comments - the core babel compiler ships as a peer dependency in this plugin. In case the core lib is not being pulled down via another dep in your repo, ensure this is installed on your end.
Looking at the peer dependency in gulp-babel the author is specifying #babel/core (7.x). Though, the slightly older babel-core (6.x) will work as well. My guess is the author (who is the same for both projects) is in the midsts of reorganizing their module naming. Either way, both npm installation endpoints point to https://github.com/babel/babel/tree/master/packages/babel-core, so you'll be fine with either of the following...
npm install babel-core --save-dev
or
npm install #babel/core --save-dev

The accepted answer doesn't really answer how to minify straight es6. If you want to minify es6 without transpiling, gulp-uglify v3.0.0 makes that possible:
Update March 2019
Using my original answer, you definitely want to replace the uglify-es package with terser, as it seems uglify-es is no longer being maintained.
Original answer, still works:
1.) First, upgrade your gulp-uglify package to > 3.0.0 If you're using yarn and want to update to the latest version:
yarn upgrade gulp-uglify --latest
2.) Now you can use uglify-es, the "es6 version" of uglify, as so:
const uglifyes = require('uglify-es');
const composer = require('gulp-uglify/composer');
const uglify = composer(uglifyes, console);
gulp.task('compress', function () {
return gulp.src('src/*.js')
.pipe(uglify())
.pipe(gulp.dest('dist'))
});
For more info: https://www.npmjs.com/package/gulp-uglify

You actually can uglify ES6 code without transpilation. Instead of gulp-uglify plugin, use gulp-uglifyes plugin.
var gulp = require('gulp');
var rename = require('gulp-rename');
var uglify = require('gulp-uglifyes');
var plumber = require('gulp-plumber');
var plumberNotifier = require('gulp-plumber-notifier');
var sourcemaps = require('gulp-sourcemaps');
var runSequence = require('run-sequence').use(gulp);
gulp.task('minjs', function () {
return gulp.src(['/dist/**/*.js', '!/dist/**/*.min.js'])
.pipe(plumberNotifier())
.pipe(sourcemaps.init())
.pipe(uglify({
mangle: false,
ecma: 6
}))
.pipe(rename(function (path) {
path.extname = '.min.js';
}))
.pipe(sourcemaps.write('.'))
.pipe(gulp.dest('/dist'));
});

gulp-uglify:
For ES6 and newer.
install: npm install --save-dev gulp-uglify
install: npm install --save-dev gulp-babel #babel/core #babel/preset-env
Usage:
const gulp = require('gulp');
const uglify = require('gulp-uglify');
const babel = require('gulp-babel');
gulp.task('script', () => {
return gulp.src('src/**/*.js')
.pipe(babel({
presets: ['#babel/env']
}))
.pipe(uglify())
.pipe(gulp.dest('src/dist'))
});

I worked at this for a while before getting it to work. As other answers have stated the problem is that gulp-uglify doesn't support ES6. gulp-uglify-es does, however if is no longer maintained. Terser is recommended by others, but it doesn't play well with gulp and using it with pipe().
If you use gulp-uglify as I do your gulpfile.js looks something like:
var uglify = require('gulp-uglify');
const html2js = () => {
var source = gulp.src(config.appFiles.templates);
return source
.pipe(concat('templates-app.js'))
.pipe(uglify())
.pipe(gulp.dest(config.buildDir));
};
You can however use the gulp-terser package, which is very easy to just replace and get the same functionality:
var terser = require('gulp-terser');
const html2js = () => {
var source = gulp.src(config.appFiles.templates);
return source
.pipe(concat('templates-app.js'))
.pipe(terser())
.pipe(gulp.dest(config.buildDir));
};

Using gulp-uglify-es instead of gulp-uglify helped me perfectly to accomplish same as you're asking for

The current (Nov 2021) easiest way to transpile and uglify is to use gulp-terser.
If you're already using gulp-uglify then just install gulp-terser and change "uglify" with "terser" and you're done.
const uglifyes = require('terser');
gulp.task('compress', function () {
return gulp.src('src/*.js')
.pipe(terser())
.pipe(gulp.dest('dist'))
});

unfortunately, as per now, you can't use uglify with es-next code,
you can:
Transpile to ES5using Babel
Use Babili instead of Uglify.

module.exports = {
...
optimization: {
minimize: true
},
...
}
webpack can do the job

Gulp and Babel: Error: Cannot find module

I have a project that I've set up using gulp and babel. Everything is working fine, except when I create a module and import it once it's converted from ES6 to ES6 it doesn't work. I get an error:
Error: Cannot find module 'hello.js'
at Function.Module._resolveFilename (module.js:440:15)
at Function.Module._load (module.js:388:25)
at Module.require (module.js:468:17)
Here's my gulpfile.babel.js:
import gulp from "gulp";
import babel from "gulp-babel"
import concat from "gulp-concat"
const dirs = {
src: "src",
dest: "build"
}
gulp.task("build", () => {
return gulp.src(dirs.src + "/**/*.js")
.pipe(babel())
.pipe(concat("build.js"))
.pipe(gulp.dest(dirs.dest))
});
gulp.task("default", ["build"]);
During build everything is concatenated into one file. Under src/ I have:
app.js
hellojs
app.js
import hello from './hello.js'
console.log(hello());
hello.js
export default () => {
return 'Hey from hello.js';
};
And I run like so:
npm start
Which basically calls node ./build/build.js.
I think it's because it's concatenating the ES6 into ES5 and the bundle.js still contains the require for hello.js. It wont find it though because its concatenated. Is that possible?

It is incorrect to concatenate two module files and expect the program to work properly, even when transpiled to ES5. Bundling involves more than concatenating the scripts: each module needs a closure for registering exports and resolving the contents of other modules.
You must instead use a bundling tool such as Browserify, Webpack or Rollup. Here's how one would bundle with Browserify (which in this case, it is easier to rely on the Babelify transform rather than gulp-babel):
var browserify = require('browserify');
var gulp = require('gulp');
var source = require('vinyl-source-stream');
var babelify = require('babelify');
gulp.task('browserify', function() {
return browserify({
entries: './src/app.js'
})
.transform(babelify)
.bundle()
.pipe(source('bundle.js'))
.pipe(gulp.dest('./build/'));
});

Gulp-sourcemap, browserify and babelify

I'm writing a react app using gulp to build and babelify to transpile.
I use the following definition of browserify task :
gulp.task('browserify', function() {
var entries = glob.sync('./app/**/*.js*');
var bundler = browserify({entries: entries, debug: true})
.transform("babelify", {presets: ["es2015", "react"]})
.bundle()
.on('error', function(err) {
console.error(err);
})
.pipe(source('bundle.js'))
.pipe(buffer())
.pipe(sourcemaps.init({loadMaps: true}))
.pipe(sourcemaps.write('./'))
.pipe(gulp.dest('dist'));
});
I get one bundle.js while I expect to see transpiled js files in dist with the same folder structure as src (here app).
Am I expecting a right thing ? If yes, how can I make it to work like what I expect.

you should remove
.pipe(sourcemaps.init({loadMaps: true}))
.pipe(sourcemaps.write('./'))
which are useless while you are using debug: true on browserify.
the debug: true option writes directly the sourcemaps on bundle.js with base64 encoding. So on your browser, you get source files separatly.

Combining gulp-crisper with gulp-webpack

I'm setting up my environment to develop a polymer 1.0 application using ES6/babel.
I also want to integrate webpack, so that I can use import statements in my javascript code.
I use gulp as a build tool. This is a (simplified) gulpfile for my project:
var gulp = require('gulp');
var gulpif = require('gulp-if');
var crisper = require('gulp-crisper');
var webpack = require('gulp-webpack');
gulp.task('default', function() {
gulp.src('src/*.html')
.pipe(gulpif('*.html', crisper()))
.pipe(gulpif('*.js', webpack({
loaders: [
{
test: /\.js$/,
exclude: [/node_modules/],
loader: 'babel-loader?sourceMap=true'
}
]
})))
.pipe(gulp.dest('dist'));
});
This works if I use gulp-babel instead of gulp-webpack. But so I get the following error:
[10:28:38] Using gulpfile E:\Dokumente\polymer\test-gulp-webpack\gulpfile.js
[10:28:38] Starting 'default'...
[10:28:38] Finished 'default' after 225 ms
[10:28:38] Version: webpack 1.12.2
ERROR in Entry module not found: Error: Cannot resolve 'file' or 'directory' E:\Dokumente\polymer\test-gulp-webpack\src\index.js in E:\Dokumente\polymer\test-gulp-webpack
The src directory contains only a index.html with the following content:
<html>
<body>
<h1>TEST</h1>
<script>
var test = "TEST";
</script>
</body>
</html>
Any suggestion how I can fix this? Maybe tell crisper to temporarily write the javascript to the filesystem? Or maybe use some fancy loader for webpack?