Source code of the codelab (How to Contribute to the Web Components ecosystem)[https://codelabs.developers.google.com/codelabs/web-components-how-to-contribute/]
Given a current and previous value, it computes the difference and renders a symbol.
<my-element current="10" previous="0"></my-element>
First, make sure you have the Polymer CLI installed. Then run polymer serve
to serve your element locally.
$ polymer serve
$ polymer test
Your application is already set up to be tested via web-component-tester. Run polymer test
to run your application's test suite locally.