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Direct class compatibility (#146)

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* drop support for attributes and move class compatibility into factory

* fix docs

* bring back attributes for now

* forgot attribute change in class, don't load shim

* delete native-shim file

* make it more minification-friendly

* fix docs

* no need for method names
This commit is contained in:
Luke Westby 2018-10-30 16:26:27 -07:00 committed by GitHub
parent 4309dd85d1
commit aac0c1febc
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 103 additions and 235 deletions
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173
lib/CustomElement.js
View File

@ -3,27 +3,7 @@
*/
// Return a function for making an event based on what the browser supports.
// IE11 doesn't support Event constructor, and uses the old Java-style
// methods instead
function makeMakeEvent() {
try {
// if calling Event with new works, do it that way
var testEvent = new CustomEvent('myEvent', { detail: 1 })
return function makeEventNewStyle(type, detail) {
return new CustomEvent(type, { detail: detail })
}
} catch (_error) {
// if calling CustomEvent with new throws an error, do it the old way
return function makeEventOldStyle(type, detail) {
var event = document.createEvent('CustomEvent')
event.initCustomEvent(type, false, false, detail)
return event
}
}
}
/**
/**
* Create a DOM Event without worrying about browser compatibility
*
* @param {string} eventName The name of the event to create
@ -35,6 +15,8 @@ function makeMakeEvent() {
*/
exports.makeEvent = makeMakeEvent()
var makeClass = makeMakeClass()
function noOp() {}
/**
@ -63,6 +45,21 @@ function noOp() {}
* this._button = document.createElement('button')
* },
*
* // Let the custom element runtime know that you want to be notified of
* // changes to the `hello` attribute
* observedAttributes: ['hello'],
*
* // Do any updating when an attribute changes on the element. Note the
* // difference between attributes and properties of an element (see:
* // https://javascript.info/dom-attributes-and-properties). This is a
* // proxy for `attributeChangedCallback` (see:
* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks).
* // Takes the name of the attribute that changed, the previous string value,
* // and the new string value.
* onAttributeChange: function(name, previous, next) {
* if (name === 'hello') this._hello = next
* },
*
* // Do any setup work after the element has been inserted into the DOM.
* // Takes no arguments. This is a proxy for `connectedCallback` (see:
* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks)
@ -79,21 +76,6 @@ function noOp() {}
* document.removeEventListener('click', this._onDocClick)
* },
*
* // Let the custom element runtime know that you want to be notified of
* // changes to the `hello` attribute
* observedAttributes: ['hello'],
*
* // Do any updating when an attribute changes on the element. Note the
* // difference between attributes and properties of an element (see:
* // https://javascript.info/dom-attributes-and-properties). This is a
* // proxy for `attributeChangedCallback` (see:
* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks).
* // Takes the name of the attribute that changed, the previous string value,
* // and the new string value.
* onAttributeChange: function(name, previous, next) {
* if (name === 'hello') this._hello = next
* },
*
* // Set up properties. These allow you to expose data to Elm's virtual DOM.
* // You can use any value that can be encoded as a `Json.Encode.Value`.
* // You'll often want to implement updates to some visual detail of your element
@ -120,7 +102,7 @@ function noOp() {}
* alert('document clicked')
* },
* _onButtonClick: function() {
* alert("clicked on #{@_hello} button")
* alert('clicked on ' + this._hello + ' button')
* }
* }
* })
@ -130,44 +112,95 @@ exports.create = function create(config) {
throw Error('Custom element with tag name ' + config.tagName + ' already exists.')
}
config.methods = config.methods || {}
config.properties = config.properties || {}
var observedAttributes = config.observedAttributes || []
var methods = config.methods || {}
var properties = config.properties || {}
var initialize = config.initialize || noOp
var onConnect = config.onConnect || noOp
var onDisconnect = config.onDisconnect || noOp
var onAttributeChange = config.onAttributeChange || noOp
function CustomElementConstructor() {
// This is the best we can do to trick modern browsers into thinking this
// is a real, legitimate class constructor and not a plane old JS function.
var _this = HTMLElement.call(this) || this
if (typeof config.initialize === 'function') {
config.initialize.call(_this)
}
for (var key in config.methods) {
if (!config.methods.hasOwnProperty(key)) continue
var method = config.methods[key]
if (typeof method !== 'function') continue
_this[key] = method.bind(_this)
}
Object.defineProperties(_this, config.properties)
return _this
var Class = makeClass()
for (var key in methods) {
if (!methods.hasOwnProperty(key)) continue
Class.prototype[key] = methods[key]
}
// Some browsers respect this in various debugging tools.
CustomElementConstructor.displayName = '<' + config.tagName + '> custom element'
Object.defineProperties(Class.prototype, properties)
CustomElementConstructor.prototype = Object.create(HTMLElement.prototype)
CustomElementConstructor.prototype.constructor = CustomElementConstructor
CustomElementConstructor.prototype.connectedCallback = config.onConnect
CustomElementConstructor.prototype.disconnectedCallback = config.onDisconnect
CustomElementConstructor.prototype.attributeChangedCallback = config.onAttributeChange
if (config.observedAttributes) {
var observedAttributes = config.observedAttributes
Object.defineProperty(CustomElementConstructor, 'observedAttributes', {
get: function() { return observedAttributes }
Class.prototype.connectedCallback = onConnect
Class.prototype.disconnectedCallback = onDisconnect
Class.prototype.attributeChangedCallback = onAttributeChange
if (Array.isArray(observedAttributes)) {
Object.defineProperty(Class, 'observedAttributes', {
get: function () { return observedAttributes }
})
}
customElements.define(config.tagName, CustomElementConstructor)
Class.displayName = '<' + config.tagName + '> custom element'
customElements.define(config.tagName, Class)
}
/**
* Attempt to make an ES6 class using the Function constructor rather than
* ordinary class syntax. The string we pass to the Function constructor is
* static so there is no script injection risk. It allows us to catch
* syntax errors at runtime for older browsers that don't support class and
* fall back to an ES5 constructor function.
*/
function makeMakeClass() {
try {
return new Function([
"return class extends HTMLElement {",
" constructor() {",
" super()",
" for (var key in this) {",
" var value = this[key]",
" if (typeof value !== 'function') continue",
" this[key] = value.bind(this)",
" }",
" }",
"}",
].join("\n"))
} catch (e) {
return function () {
function Class() {
// This is the best we can do to trick modern browsers into thinking this
// is a real, legitimate class constructor and not a plane old JS function.
var _this = HTMLElement.call(this) || this
for (var key in _this) {
var value = _this[key]
if (typeof value !== 'function') continue
_this[key] = value.bind(_this)
}
return _this
}
Class.prototype = Object.create(HTMLElement.prototype)
Class.prototype.constructor = Class
return Class
}
}
}
/**
* Return a function for making an event based on what the browser supports.
* IE11 doesn't support Event constructor, and uses the old Java-style
* methods instead
*/
function makeMakeEvent() {
try {
// if calling Event with new works, do it that way
var testEvent = new CustomEvent('myEvent', { detail: 1 })
return function makeEventNewStyle(type, detail) {
return new CustomEvent(type, { detail: detail })
}
} catch (_error) {
// if calling CustomEvent with new throws an error, do it the old way
return function makeEventOldStyle(type, detail) {
var event = document.createEvent('CustomEvent')
event.initCustomEvent(type, false, false, detail)
return event
}
}
}

164
styleguide-app/assets/custom-elements/native-shim.js
View File

@ -1,164 +0,0 @@
/**
* @license
* Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
* This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
* The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
* The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
* Code distributed by Google as part of the polymer project is also
* subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/
/**
* This shim allows elements written in, or compiled to, ES5 to work on native
* implementations of Custom Elements.
*
* ES5-style classes don't work with native Custom Elements because the
* HTMLElement constructor uses the value of `new.target` to look up the custom
* element definition for the currently called constructor. `new.target` is only
* set when `new` is called and is only propagated via super() calls. super()
* is not emulatable in ES5. The pattern of `SuperClass.call(this)`` only works
* when extending other ES5-style classes, and does not propagate `new.target`.
*
* This shim allows the native HTMLElement constructor to work by generating and
* registering a stand-in class instead of the users custom element class. This
* stand-in class's constructor has an actual call to super().
* `customElements.define()` and `customElements.get()` are both overridden to
* hide this stand-in class from users.
*
* In order to create instance of the user-defined class, rather than the stand
* in, the stand-in's constructor swizzles its instances prototype and invokes
* the user-defined constructor. When the user-defined constructor is called
* directly it creates an instance of the stand-in class to get a real extension
* of HTMLElement and returns that.
*
* There are two important constructors: A patched HTMLElement constructor, and
* the StandInElement constructor. They both will be called to create an element
* but which is called first depends on whether the browser creates the element
* or the user-defined constructor is called directly. The variables
* `browserConstruction` and `userConstruction` control the flow between the
* two constructors.
*
* This shim should be better than forcing the polyfill because:
* 1. It's smaller
* 2. All reaction timings are the same as native (mostly synchronous)
* 3. All reaction triggering DOM operations are automatically supported
*
* There are some restrictions and requirements on ES5 constructors:
* 1. All constructors in a inheritance hierarchy must be ES5-style, so that
* they can be called with Function.call(). This effectively means that the
* whole application must be compiled to ES5.
* 2. Constructors must return the value of the emulated super() call. Like
* `return SuperClass.call(this)`
* 3. The `this` reference should not be used before the emulated super() call
* just like `this` is illegal to use before super() in ES6.
* 4. Constructors should not create other custom elements before the emulated
* super() call. This is the same restriction as with native custom
* elements.
*
* Compiling valid class-based custom elements to ES5 will satisfy these
* requirements with the latest version of popular transpilers.
*/
(() => {
'use strict';
// Do nothing if `customElements` does not exist.
if (!window.customElements) return;
const NativeHTMLElement = window.HTMLElement;
const nativeDefine = window.customElements.define;
const nativeGet = window.customElements.get;
/**
* Map of user-provided constructors to tag names.
*
* @type {Map<Function, string>}
*/
const tagnameByConstructor = new Map();
/**
* Map of tag names to user-provided constructors.
*
* @type {Map<string, Function>}
*/
const constructorByTagname = new Map();
/**
* Whether the constructors are being called by a browser process, ie parsing
* or createElement.
*/
let browserConstruction = false;
/**
* Whether the constructors are being called by a user-space process, ie
* calling an element constructor.
*/
let userConstruction = false;
window.HTMLElement = function() {
if (!browserConstruction) {
const tagname = tagnameByConstructor.get(this.constructor);
const fakeClass = nativeGet.call(window.customElements, tagname);
// Make sure that the fake constructor doesn't call back to this constructor
userConstruction = true;
const instance = new (fakeClass)();
return instance;
}
// Else do nothing. This will be reached by ES5-style classes doing
// HTMLElement.call() during initialization
browserConstruction = false;
};
// By setting the patched HTMLElement's prototype property to the native
// HTMLElement's prototype we make sure that:
// document.createElement('a') instanceof HTMLElement
// works because instanceof uses HTMLElement.prototype, which is on the
// ptototype chain of built-in elements.
window.HTMLElement.prototype = NativeHTMLElement.prototype;
const define = (tagname, elementClass) => {
const elementProto = elementClass.prototype;
const StandInElement = class extends NativeHTMLElement {
constructor() {
// Call the native HTMLElement constructor, this gives us the
// under-construction instance as `this`:
super();
// The prototype will be wrong up because the browser used our fake
// class, so fix it:
Object.setPrototypeOf(this, elementProto);
if (!userConstruction) {
// Make sure that user-defined constructor bottom's out to a do-nothing
// HTMLElement() call
browserConstruction = true;
// Call the user-defined constructor on our instance:
elementClass.call(this);
}
userConstruction = false;
}
};
const standInProto = StandInElement.prototype;
StandInElement.observedAttributes = elementClass.observedAttributes;
standInProto.connectedCallback = elementProto.connectedCallback;
standInProto.disconnectedCallback = elementProto.disconnectedCallback;
standInProto.attributeChangedCallback = elementProto.attributeChangedCallback;
standInProto.adoptedCallback = elementProto.adoptedCallback;
tagnameByConstructor.set(elementClass, tagname);
constructorByTagname.set(tagname, elementClass);
nativeDefine.call(window.customElements, tagname, StandInElement);
};
const get = (tagname) => constructorByTagname.get(tagname);
// Workaround for Safari bug where patching customElements can be lost, likely
// due to native wrapper garbage collection issue
Object.defineProperty(window, 'customElements',
{value: window.customElements, configurable: true, writable: true});
Object.defineProperty(window.customElements, 'define',
{value: define, configurable: true, writable: true});
Object.defineProperty(window.customElements, 'get',
{value: get, configurable: true, writable: true});
})();

1
styleguide-app/index.html
View File

@ -6,7 +6,6 @@
<link href="assets/reset.css" rel="stylesheet">
<link href="https://fonts.googleapis.com/css?family=Muli:400,400i,600,600i,700,700i,800,800i,900,900i" rel="stylesheet">
<script src="assets/custom-elements/custom-elements.min.js"></script>
<script src="assets/custom-elements/native-shim.js"></script>
<script src="assets/generated_svgs.js"></script>
<script src="javascript.js"></script>
</head>