Write Polymer 1.0 elements as TypeScript @decorated classes
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README.md

PolymerTS

Write Polymer 1.x elements as TypeScript @decorated classes.

NOTE: If you need to support Polymer 2.x or higher, see the official PolymerDecorators project. We will be working on providing a migration path for users that are currently using Polymer 1.0 and PolymerTS. To find out more (or help!), see issue #110.

Table of contents

Installation

Install via bower:

bower install -save polymer-ts

You'll get the following files in bower_components/polymer-ts:

  • polymer-ts.html the html file to include via <link rel="import"> that loads PolymerTS
  • polymer-ts.min.html the html file to include via <link rel="import"> that loads PolymerTS (minified version)
  • polymer-ts.d.ts the file to reference in your TypeScript code (/// <reference path="...">)
  • polymer-ts.ts the source TypeScript file for debugging purposes
  • polymer-ts.js or polymer-ts.min.js the JavaScript file if you want to include PolymerTS via <script src="">

Supported features

  • Decorators
    • @component(tagName) sets component's name (equivalent to is: in PolymerJS)
    • @extend(name) extends a native tag (equivalent to extends: in PolymerJS)
    • @hostAttributes(attrs) sets host attributes (equivalent to hostAttributes: in PolymerJS)
    • @property(defs) sets a property (equivalent to properties: in PolymerJS)
    • @observe(propList) sets an observer function on single or multiple properties (equivalent to observers: in PolymerJS)
    • @computed() defines a computed property
    • @listen(eventName) sets an event listener function (equivalent to listeners: in PolymerJS)
    • @behavior(className) gets the behaviors of the class (equivalent to behaviors: in PolymerJS)
  • Registration functions
    • className.register() registers in Polymer
    • className.register(true) registers in Polymer but not in document.registerElement()
    • className.create() creates an instance of the element
  • Other
    • class constructor mapped to factory constructor (factoryImpl())

Unsupported:

  • property defined with getter/setter

How to write elements

  1. Write elements as TypeScript classes
  2. Extend the polymer.Base class
  3. Use @decorators as needed

A class-element:

  • can have private properties/fields
  • can use class constructor (rendered as factoryImpl())
  • can use inherited properties and methods
  • can use TypeScript Mixins

How to correctly reference in markup

In the head section of your main .html file:

<head>
   <!-- webcomponents, polymer standard, polymer-ts -->
   <script src="bower_components/webcomponentsjs/webcomponents-lite.js"></script>
   <link rel="import" href="bower_components/polymer/polymer.html">
   <link rel="import" href="bower_components/polymer-ts/polymer-ts.html">

   <!-- your custom elements -->
   <link rel="import" href="elements/my-element.html">

   <!-- your application -->
   <script src="myapp.js"></script>
</head>

In your custom element (e.g. elements/my-element.html):

<dom-module id="my-element">
   <!-- ... your custom element here... -->
</dom-module>

<!-- your element code typescript transpiled file -->
<script type="text/javascript" src="my-element.js"></script>

In your element typescript code (e.g. elements/my-element.ts):

/// <reference path="../bower_components/polymer-ts/polymer-ts.d.ts" />

@component("my-element")
class MyElement extends polymer.Base
{
}

// after the element is defined, we register it in Polymer
MyElement.register();

The above example loads in the following order:

  • WebComponents
  • Polymer
  • PolymerTS
  • Your custom elements
  • Your app

Note: due to an issue in WebComponents, you can't use the <script> tag on the main page to load PolymerTS or custom elements, you have always to use the <link rel="import"> syntax.

This will make sure that scripts will be loaded in the correct order in all browsers.

If for some reason you want to use script inclusion for your elements, you have to load Polymer and PolymerTS via script too. Polymer doesn't have a polymer.js file (it's shipped as .html only), but you can get one from greenify/polymer-js.

Starting the application

Any global code in your app that depends on Polymer should be started only after the event WebComponentsReady has been fired:

window.addEventListener('WebComponentsReady', (e) =>
{
   // any code that depends on polymer here
});

Using the yeoman generator to create new elements

New elements can be quickly scaffolded using the polymerts:el yeoman generator available with the package generator-polymerts.

First install yeoman and generator-polymerts:

npm install -g yo
npm install -g generator-polymerts

then use the polymerts:el generator to create a new element:

yo polymerts:el my-element

Decorators explained

@component(tagName)

Sets the tag name of the custom component. The decorator is applied on the class keyword. Tag names must include a - as per WebComponents specs.

Example of a <my-element>:

@component("my-element")
class MyElement extends polymer.Base
{
}

If the component extends a native HTML tag, pass the "base" tag name as second argument (alternatively, use the @extend decorator)

@component("my-button","button")
class MyButton extends polymer.Base
{
}

@extend(tagName)

Specifies that the element is an extension of a native HTML element.

@component("my-button")
@extend("button")
class MyButton extends polymer.Base
{
}

@property(def)

Creates a Polymer property. It can be applied to a member field or a function. When applied to a function, the property becomes a computed property.

The parameter def is a map object that sets the options for the property:

{
    type?: any;                     // Boolean, Date, Number, String, Array or Object
    value?: any;                    // default value for the property
    reflectToAttribute?: boolean;   // should the property reflect to attribute
    readonly?: boolean;             // marks property as read-only
    notify?: boolean;               // if set to true, will trigger "propname-changed"
    computed?: string;              // computed function call (as string)
    observer?: string;              // observer function call (as string)
}

Examples:

@property({ type: number, value: 42 }) // Polymer initialization (preferred)
initialValue: number;

The default value for a property is optional as long as the property is initialized:

@property()
myprop = 42;  // direct initialization

or

@property({ type: number })
myprop: number;

constructor() {
   this.myprop = 42; // initialized within constructor; called after Polymer initialization
}

NOTE: If you use direct initialization, the property will be set after the ready() method is called. If you use the value attribute of the @property decorator, it will be called before ready().

NOTE: If you're creating a readOnly property, use Polymer initialization. If you use direct initialization, Polymer will overwrite your value with undefined.

@property({type: number, value: 42})
myprop: number;  // will be initialized with value before ready() is called

While you can specify computed and observer in a property definition, there are the specific decorators @computed and @observe that are easier to use.

@observe(propList)

Sets an observer function for a single property or a list of properties.

If observing a single property, the function must be of the type function(newVal,OldVal).

If observing multiple properties (comma separated), the function receives only the new values, in the same order of the list.

// single property observer
@observe("name")
nameChanged(newName,oldName)
{
   // ...
}

NOTE: Only one single-property observer is supported for the same property name. If you have multiple single-property observers registered with the same property, only the last one one will be used (you will not get an error).

// multiple property observer
@observe("firstname,lastname")
fullnameChanged(newFirstName,newLastName)
{
   // ...
}

@computed

Creates a computed property or sets the function for a computed property.

The easiest way is to decorate a function that takes as arguments the properties that are involved in the computed property.

In the following example, a computed property named "fullname" is created, based on the properties "firstName" and "lastName":

@computed()
fullname(firstName,lastName)
{
   return firstName+" "+lastName; // firstname is the same as this.firstName
}

The decorator accepts also a map object for setting options on the property, e.g.:

@computed({ type: String })
fullname(firstName,lastName)
{
   return firstName+" "+lastName;
}

The @computed decorator is a shortcut for @property:

@property({computed: 'computefullname(firstName,lastName)'})
fullname: string;

computefullname(firstName,lastName)
{
   return firstName+" "+lastName;
}

@listen(eventName)

Sets a listener function for an event.

In the following example the function resetCounter() is called whenever the event reset-counters is triggered (e.g. via fire()).

   @listen("reset-counters")
   resetCounter() {
      this.count = 0;
   }

@behavior(className)

Incorporates behaviors from another object.

The object can be either a class (not necessarily a PolymerTS element) or a plain JavaScript object.

The @behavior decorator can decorate the class keyword or it can be put within the class itself.

Examples:

class MyBehavior extends polymer.Base
{
   @listen("something_has_happened")
   onBehave() {
      console.log("something_has_happened triggered");
   }
}
@component("my-element")
@behavior(MyBehavior)
class MyElement extends polymer.Base
{
  // ...
}

or

@component("my-element")
class MyElement extends polymer.Base
{
	@behavior(MyBehavior)
	// ...
}

Note: a functionality similar to @behavior can be also obtained by plain class inheritance or by the use of Mixins.

Writing elements only with code

It's also possible to create elements using TypeScript code only, without having any external .html. That can be useful if you want to keep template and logic in the same TypeScript file.

Use the tags @template and @style to specify the element's template and style, as in the following example:

@component("my-example")

// pass as argument what would be within <dom-module> and </dom-module>
@template(`<div>This element has been created completely from code</div>`)

// pass as argument what would be within <style> and </style>
@style(`:host { display: block; } div { color: red; }`)

class MyExample extends polymer.Base
{
   // ...
}

MyExample.register();

@hostAttributes(attributesObject)

Sets attributes on the host element.

In the following example, the style attribute of the host element is changed:

@component("my-element")
@hostAttributes({ style: "color: red;" })
class MyElement extends polymer.Base
{
}

Writing elements without using decorators

It's possible to avoid the use of decorators (e.g. for compatibility with TypeScript < 1.5) by simply writing their respective equivalent in plain Polymer syntax. E.g.

class MyElement extends polymer.Base
{
   is = "my-element";

   properties = {
      myprop: { value: 42 }
   };

   // ...
}

Examples

A timer-based counter element

@component("my-timer")
class MyTimer extends polymer.Base
{
   @property({ type: Number, value: 0 })
   public start: number;

   public count: number;

   private timerHandle: number;

   constructor() {
      this.count = this.start;
      this.timerHandle = setInterval(() => {
         this.count++;
      }, 1000);
   }

   @observe("count")
   countChanged(newValue, oldValue) {
      if(newValue==100000) {
         console.log("too much time spent doing nothing!");
         this.fire("reset-counters");
	  }
   }

   @listen("reset-counters")
   resetCounter() {
      this.count = 0;
   }

   detatched() {
      clearInterval(this.timerHandle);
   }
}

MyTimer.register();
<dom-module id="my-timer">
   <template>
      <p>This is a timer element, and the count which started
      from <span>{{start}}</span> is now: <span>{{count}}</span></p>
   </template>
</dom-module>

To use the element

<my-timer start="42"></my-timer>

Using computed properties

There are several (almost equivalent) ways of defining a computed property:

// classic way
@property({name: "fullname", computed: "computeFullName(first,last)"});
fullname: string;
computeFullName(f,l) {
   return f+" "+l;
}

// by decorating a function
@property({computed: "first,last"});
fullname(f,l) {
   return f+" "+l;
}

// by using @computed, name and parameters extracted from the function
@computed
fullname(first,last) {
   return first+" "+last;
}

Using custom constructor

Elements can be instantiated by using a custom constructor:

@component("my-info")
class MyInfo extends polymer.Base
{
   private someInfo: string;

   constructor(someInfo: string) {
      this.someInfo = someInfo;
   }
}

// creates the element passing a parameter
var el = MyInfo.create("hello world");

// and attach in some way to the DOM
document.body.appendChild(el);

Using behavior defined in paper elements

This example shows how to use a behavior defined in an external library (Polymer paper elements).

/// <reference path="typings/polymer/paper/PaperRippleBehavior.d.ts"/>

@component('ts-element')
@behavior(Polymer['PaperRippleBehavior'])
class TsElement extends polymer.Base implements Polymer.PaperRippleBehavior
{   
   // stand-in properties for behavior mixins 
   noink: boolean = false;
   ensureRipple: (optTriggeringEvent?: Event) => void;
   getRipple: () => paper.PaperRipple;
   hasRipple: () => boolean;

   handleClick(e:Event)
   {
      this.greet = "Holà";      
      this.fire("greet-event");
      this.ensureRipple(e);
   }
}

What it does

In short, PolymerTS:

  • provides a class named polymer.Base that all your elements can extend
  • provides a suite of decorators to easily implement elements
  • injects the method register() in your element-class (to allow registration it in Polymer)

in turn, the register() method:

  • process decorators translating them in its Polymer counterpart
  • connects the constructor() before of the attached event so that properties are correctly initialized
  • connects the constructor(args) to the factoryImpl() callback so that custom constructor is processed correctly
  • registers the element in Polymer, saving the constructor function and making it available as the create() method

Documentation

Typically with Polymer projects you can generate documentation easily with the <iron-component-page> component. However, this component doesn't work well with PolymerTS projects because the source code is not in the same file as the HTML. You can get around this by using the polymerts-doc-generator, which outputs a version of your code that combines HTML and pure JS in one file, which can be easily consumed by <iron-component-page>.

Known issues

  • can't use property defined with get and set (Polymer's issue)
  • can't include elements using <script> on the main .html page (WebComponent's issue)

Contributing

Contributions are welcome.

If you find bugs or want to improve it, just send a pull request.

Getting Started

  1. Clone this repo
  2. Make sure you have node and bower installed.
  3. Run npm install && bower install
  4. To build, just run npm run build. During development, using the TypeScript compiler settings in your editor should work fine, as long as it points to ./tsconfig.json and uses the version of tsc installed in node_modules.

Testing

PolymerTS uses Jasmine for unit tests. Currently there isn't a test runner like Karma setup, so you'll need to manually run the tests in different browsers.

All of the tests are in the Test folder; the entry point is tests.ts.

In order to run the tests, you need a local HTTP server. If you don't have one installed, you can install http-server with the command npm install http-server -g.

Next, just point your browser to http://localhost:<port>/Test/). http-server defaults to port 8080.

Samples

There is a Samples folder with some examples, but these are not currently built or maintained.

Change log

Older versions:

  • v0.2.0 (Apr 18, 2017)
    • Fix: allow access/modify styles (override prototype.style)
  • v0.1.28 (Aug 8, 2016)
    • Added unlisten() to API
  • v0.1.19 (Sep 16, 2015)
    • Extended @behavior to work with plain JavaScript objects (in addition to TypeScript classes)
  • v0.1.17 (Sep 14, 2015)
    • BREAKING CHANGE: (mostly harmless) Polymer.Base is now an extension of HTMLElement
    • Added is to Element's interface
  • v0.1.7 (Aug 7, 2015)
    • Corrected signature for Polymer.dom.flush()
  • v0.1.6 (Jul 21, 2015)
    • provided polymer-ts.d.ts to reference from external projects
    • no longer need to include webcomponents.js (non-lite) in IE
  • v0.1.5 (Jul 18, 2015)
    • BREAKING CHANGE: global functions createElement() and createClass() deprecated, use Element.resgister() instead
    • BREAKING CHANGE: use <link rel="import"> to load PolymerTS and custom elements
  • v0.1.4 (Jul 17, 2015)
    • register elements with className.register()
  • v0.1.3 (Jul 16, 2015)
    • polymer.Base is now seen as a full ES6 inheritable class
  • v0.1.2 (Jul 13, 2015)
    • Improved the way objects are instatiated
    • support for static method create() on the element class
  • v0.1.1 (Jul 10, 2015)
    • Added support for constructor() with parameters.
    • constructor() is now a replacement of factoryImpl().
    • preamble implements polymer.Element no longer required
  • v0.1.0 (Jul 10, 2015)
    • Added support for class inheritance
    • Added support for use of constructor()
    • Added support for decorator-less syntax
  • v0.0.1 to v0.0.9
    • early experimental versions