Polymer 3.0 vs 2.0 – How to Upgrade MixIns

Since I couldn’t find this anywhere on the internet, here’s a cheat sheet:

Before:

class PaperNumberInput extends Polymer.mixinBehaviors([Polymer.PaperInputBehavior], Polymer.Element) {

 

After:

import { Element } from ‘../../node_modules/@polymer/polymer/polymer-element.js’;
import { mixinBehaviors } from ‘../../node_modules/@polymer/polymer/lib/legacy/class.js’;
import { PaperInputBehavior} from ‘../../node_modules/@polymer/paper-input/paper-input-behavior.js’;

class PaperNumberInput extends mixinBehaviors([PaperInputBehavior], Element) {