Currently my org is on Polymer 1 with Selenium, Protractor and Mocha and we use the shady dom. For acceptance tests we use the /deep/ combinator to pierce the DOM. With polymer 2 the /deep/ combina...

How can I use Polymer 2 elements in Polymer 3 element? The following doesn't work since <link> element doesn't work inside shadow dom. static get template() { return ' <link rel="import...

We have a huge Polymer 1.0 project with a few hundred elements and are wondering whats the best way to upgrade everything to 3.0. Should we upgrade to 2.0 first or directly go to 3.0? Also are ther...

I am using the vaadin-grid-filter with Polymer 2.x and I am facing the following problem. I have a vaadin-grid-column as following, <vaadin-grid-column width="15em"> <template class="hea...

I am developing a web component using Polymer v3, and need to include some custom elements defined in legacy Polymer 2 components in the template HTML of my new component. Since HTML imports are ...

I am working in web application project which is made in Polymer 2.0, All Custom elements extends some Mixins. Some of those Mixins just provide utility functions to custom elements just like Date ...

I'm facing this issue while running polymer init on polymer-cli. Uncaught DOMException: Failed to execute 'define' on 'CustomElementRegistry'

I am struggling with getting out of the current situation: we have a polymer SPA (A) deployed on a certain server and bound to a certain url: http://example.com/A, we do need to show legacy pages o...

I am trying to create a component that does not have a Shadow DOM. Yeah, I know, Shadow DOM is great and all and is one of the main focuses of Web Components. But, let's say I wanted a component's ...

I've successfully built a number of Polymer 2.0 elements and they run great in ES6 capable browsers. When I try to transpile them to ES5, the browser throws a bunch of errors, like these: Failed ...

I am attempting to build generic web components that render JSON object collections, like a tree view and a multi-list view (moving items between two lists). I would like to copy the pattern used b...

I am experimenting with Polymer 2.x and what I don't understand is how to use Polymers own behaviors in Polymer 2.x, iron-resizable-behavior as an example. The Polymer 2.0 upgrade guide tells us ...

Hey whats the right way to add a transition to iron-pages? At the moment i just create a custom-element, a "clone" of iron-pages and add the iron-selectable behavior. I use css transitions on the e...

I would like to develop some of the webcomponents in a Polymer 2.0 project with scala.js. While there is a wonderful demo-project on github demonstrating how it works with Polymer 1.0. I cannot get...

I'm testing my Polymer application and I get a pretty good score on Lighthouse. However, I still have a small problem. I have a manifest.json file containing everything so the app can be added to t...

I've been trying to make a simple iron-ajax post to the server, but it keeps failing at the preflight call. For the life of me I can't figure out what's going on, all the CORS headers seem to be co...

I want a custom element I'm defining to have the Polymer.IronScrollTargetBehavior in Polymer 2. In Polymer 1, this can be done by adding it to the behaviors array: Polymer({ is: 'my-element', b...

I am trying to bind local properties.json and trying to create dynamic elements, but the problem is I am not getting any console errors and not seeing JSON in the UI. I didn't find a Polymer 2.0 e...

I'm trying to create a hybrid app using Polymer 2.0. I've used polymer-2-application and polymer-2-starter-kit sample and it was working when it is tested on safari browser. But when I run it o...

I'd like to inject a rendering template from a parent component to a child component using <slot> insertion points. The injected template contains data-binding on a property of the child comp...

I'm having such a hard time trying to use the Polymer.importHref function... What am I missing?

When I create a Polymer 2.0 element, only the ready lifecycle callback seems to fire, and I can't work out why. For example, I have this Polymer element: <link rel="import" href="../../bower_co...

I'm working with polymer 2, I download polymer paper input elements, then i add the link tag: <link rel="import" href="../bower_components/paper-input/paper-input.html"> then: <paper-i...

Simple question, but no documentation is to be found on the subject : is there a debouncer in Polymer 2.0? If so, how can it be used? this.debounce was an instance method in 1.0, but it appears to...

I'm trying to sync some of my web component properties between instances of the same element so if one of this properties changes then the same property gets updated in all the instances with the c...