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Gulp Workflows

• Wouldn't it be nice if there was a way to convert ES6 to code every browser can support? Of course!
• Wouldn't it be cool if you could include module support from Node in client side code? Certainly.
• What could do this sort of magic for us? Gulp Tasks!

Learning Objectives

By the end of this tutorial, you will understand:

• What Gulp is and what it can do
• How to install Gulp on your computer
• How to write a Gulp task and run it
• How to add use additional modules with Gulp

Introducing: Gulp

• Gulp is a software built on Node.
• It runs tasks that manipulate files on your system.
• It is an active, open-source project.
• There are many community-built plugins built to work directly with gulp.
• It is commonly used for bundling, minificiation, and ES6 support.
• Grunt is a popular alternative to Gulp.

Installing Gulp

To install Gulp, we should have a Node.js environment prepared. If you do not have one, you should visit https://nodejs.org/en/ to learn more.

1. You'll want to install gulp globally. You can do this by running the npm install gulp -g command.
2. This states that we want to use npm to install the gulp package globally (for any project to use).
3. Gulp requires that we store our tasks in a gulpfile.js. This should be in the same directory as your package.json.
4. We also need to include gulp in our project. To do that, we will run npm install gulp --save-dev.
5. Now, we should run gulp!
6. Oh no - we ran into a problem.

Using gulpfile ~/path/to/gulpfile.js
Task 'default' is not in your gulpfile
Please check the documentation for proper gulpfile formatting

Let's solve this problem by defining a Gulp task.

Defining a Gulp Task

• What is a task?
• A task is something we must do to achieve a result.
• In Gulp, we create tasks to perform tasks that can transform our code.
• A task may perform one job; it may also perform many at once.

In our gulpfile.js we need to include the gulp module. To do this, we should define a variable: var gulp = require('gulp'); This will allow us to call upon Gulp to create a task.

My First (Default) Task

After declaring our gulp variable, we should create our first task. This will require us to call upon Gulp to define a task. We must also have a name for our task. By default, Gulp requires a default task. It is the first task that Gulp will look for when reading your gulpfile.js. Let's define our first (default) task:

var gulp = require('gulp');

//define a task with the name of 'default' 
// and a callback to perform when the task is ran
gulp.task('default', function() {
  console.log('I am the default task. Hear me roar');
});

(Source)

In your terminal, run gulp. This will have the library look for a default task in your gulpfile.js. It will then execute the callback that you define for your task. The output will appear as follows:

Starting 'default'...
I am the default task. Hear me roar
Finished 'default' after 144 μs

Project: A Gulp Workflow that supports ES6 and Modules for the Web

We're going to include a few external modules to create a Gulp workflow. Our workflow will support:

• Node-style require() statements using Browserify.
• Support ES6 (ES2016) and JSX (for React.js) using Babelify (and a few Babel plugins).
• Compile individual modules together using vinyl-source-stream.

We need to install a variety of modules. The installation commands are:

• npm install --save-dev browserify
• npm install --save-dev babelify
• npm install --save-dev babel-preset-es2015 babel-preset-react
• npm install --save-dev vinyl-source-stream

We can then add our modules to our gulpfile.js:

var gulp = require('gulp');
var browserify = require('browserify');
var babelify = require('babelify');
var source = require('vinyl-source-stream');

We're all set with our dependencies. Now, it is time to create a file structure for our project. We should create a folder called source for our actual Javascript application. We'll create an app.js in that source directory. We should also create a build folder to contain our final, production-ready Javascript file.

touch source/.gitkeep build/.gitkeep source/app.js

You'll notice that there is currently no file inside of our build directory other than a .gitkeep. We should define a task that will use the installed modules to transform our code and make it usable on the front-end. We should update our gulpfile.js's default task.

gulp.task('default', function() {
  return browserify('./source/app.js')
        .transform("babelify", {presets: ["es2015", "react"]})
        .bundle()
        .pipe(source('build.js'))
        .pipe(gulp.dest('./build/'))
});

Let's identify what is going on inside of our default task:

• The task uses browserify to include our modules that are required in our source/app.js file.
• It then transforms any ES6 (ES2015) and React JSX templates into usable code on the client side. This usually translates our modern Javascript code into ES5 that most current evergreen browsers support.
• The task then bundles our files together.
• Next, the task creates a file called build.js.
• Gulp finally places the build.js inside of a destination (dest) folder of build/.
• The full version of this Gulpfile.js may be found here.

Run gulp in your terminal. Inspect the build/build.js file. What do you see?

Verifying that everything works

Let's write some ES6. We'll then use gulp to run tasks that will create a file prepared for the client side. To verify everything works, we can run the script generated in the console.

In my app.js, I want todefine an ES6 class called HelloWorld. The class should have a toString() method that returns 'Hello, world!'. I will then instantiate a new instance of the class and console log the toString() method that it contains.

// define an ES6 class called HelloWorld
class HelloWorld {
  // define a toString() method on the class
  toString() {
    return 'Hello, world!';
  }
}
// instantiate a new instance of HelloWorld
var sample = new HelloWorld();
// console.log sample's toString() method
console.log(sample.toString());

(Source)

Now, we should run gulp in the terminal. Upon completion, open the build/build.js file. It will contain a large amount of obfuscated code such as (function e(t,n,r){function s(o,u)..... Copy and paste this code into a browser's Javascript console. Inside the console, you should see Hello, world!.

Tips and Tricks

• You will need to re-run the gulp command every time you make a change.
• There is nodemon support for gulp.
• You can have gulp watch files for changes using gulp-watch.