Step 1: Set up

In this tutorial, you’ll learn how to build elements using Polymer 2.0. You’ll create a simple Polymer element, a toggle button. The finished button will look something like this:

You’ll be able to use it with simple markup like this:

<icon-toggle></icon-toggle>

This project introduces you to most of the key concepts in working with Polymer.

Don’t worry if you don’t understand everything. Each of the concepts presented here is described in detail in the Polymer documentation.

Step 1: Get set up

To follow this tutorial, you’ll need:

• git.
• The starting code, available on GitHub.
• The Polymer CLI to run the demo.

Download the starting code

1. Download the starting code by running this command:

   git clone https://github.com/PolymerLabs/polymer-2-first-element.git
   

2. Open the project folder:

   cd polymer-2-first-element
   

   Your project folder should look something like this:

   README.md
   bower.json
   demo/
   icon-toggle-finished/
   icon-toggle.html
   index.html
   

   The main file you’ll work with is icon-toggle.html, which contains the definition for your custom element.

Install Polymer CLI

Install the Polymer CLI to serve the demo locally.

Polymer CLI requires Node.js, npm, git and Bower. For full installation instructions, see the Polymer CLI documentation.

To install Polymer CLI:

npm install -g polymer-cli

Install dependencies and run the demo

To install the element's dependencies and run the demo:

1. Run bower install from the repo directory:

   bower install
   

   This installs the components and dependencies required to use the Polymer library and other web components.

   You will now see an extra folder named bower_components in the project directory:

   README.md
   bower.json
   bower_components
   demo/
   icon-toggle-finished/
   icon-toggle.html
   index.html
   

2. Run the Polymer development server from the project directory:

   polymer serve --open
   

   You’ll see some text where the icon toggles should appear. It doesn’t look very interesting, but it shows that everything is working.

   (Note that the URL includes icon-toggle—the component name listed in this element’s bower.json file—rather than the actual directory name. If you’re wondering why polymer serve does this, see HTML imports and dependency management.)

If everything looks good, move on to step 2.

Step 2: Add local DOM