mirror of
https://github.com/NoRedInk/noredink-ui.git
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207 lines
8.4 KiB
JavaScript
207 lines
8.4 KiB
JavaScript
/**
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* @module CustomElement
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*/
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/**
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* Create a DOM Event without worrying about browser compatibility
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*
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* @param {string} eventName The name of the event to create
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* @param {*} [detail] The optional details to attach to the event
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* @return {Event} A valid Event instance that can be dispatched on a DOM node
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* @example
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* var event = CustomElement.makeEvent('change', { name: this._secretInput.value })
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* this.dispatchEvent(event)
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*/
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exports.makeEvent = makeMakeEvent()
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var makeClass = makeMakeClass()
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function noOp() {}
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/**
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* Register a custom element using some straightforward and convenient configuration
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*
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* @param {Object} config
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* @param {string} config.tagName The name of the tag for which to create a custom element. Must contain at least one `-` and must not have already been defined.
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* @param {Object<string, Object>} config.properties Getters and setters for properties on the custom element that can be accessed and set with `Html.Attributes.property`. These should map a property name onto a `get` function that returns a value and a `set` function that applies a value from the only argument.
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* @param {Object<string, function>} config.methods Functions that can be invoked by the custom element from anywhere. These methods are automatically bound to `this`.
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* @param {function} config.initialize Method invoked during setup that can be used to initialize internal state. This function is called whenever a new instance of the element is created.
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* @param {function} config.onConnect Method invoked whenever the element is inserted into the DOM.
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* @param {function} config.onDisconnect Method invoked whenever the element is removed from the DOM.
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* @param {function} config.onAttributeChange Method invoked whenever an observed attribute changes. Takes 3 arguments: the name of the attribute, the old value, and the new value.
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* @param {string[]} config.observedAttributes List of attributes that are watched such that onAttributeChange will be invoked when they change.
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* @example
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* CustomElements.create({
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* // This is where you specify the tag for your custom element. You would
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* // use this custom element with `Html.node "my-custom-tag"`.
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* tagName: 'my-cool-button',
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*
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* // Initialize any local variables for the element or do whatever else you
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* // might do in a class constructor. Takes no arguments.
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* // NOTE: the element is NOT in the DOM at this point.
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* initialize: function() {
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* this._hello = 'world'
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* this._button = document.createElement('button')
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* },
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*
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* // Let the custom element runtime know that you want to be notified of
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* // changes to the `hello` attribute
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* observedAttributes: ['hello'],
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*
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* // Do any updating when an attribute changes on the element. Note the
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* // difference between attributes and properties of an element (see:
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* // https://javascript.info/dom-attributes-and-properties). This is a
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* // proxy for `attributeChangedCallback` (see:
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* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks).
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* // Takes the name of the attribute that changed, the previous string value,
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* // and the new string value.
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* onAttributeChange: function(name, previous, next) {
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* if (name === 'hello') this._hello = next
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* },
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*
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* // Do any setup work after the element has been inserted into the DOM.
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* // Takes no arguments. This is a proxy for `connectedCallback` (see:
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* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks)
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* onConnect: function() {
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* document.addEventListener('click', this._onDocClick)
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* this._button.addEventListener('click', this._onButtonClick)
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* this.appendChild(this._button)
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* },
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*
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* // Do any teardown work after the element has been removed from the DOM.
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* // Takes no arguments. This is a proxy for `disconnectedCallback` (see:
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* // https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Using_the_lifecycle_callbacks)
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* onDisconnect: function() {
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* document.removeEventListener('click', this._onDocClick)
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* },
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*
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* // Set up properties. These allow you to expose data to Elm's virtual DOM.
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* // You can use any value that can be encoded as a `Json.Encode.Value`.
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* // You'll often want to implement updates to some visual detail of your element
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* // from within the setter of a property that controls it. Handlers will be
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* // automatically bound to the correct value of `@`, so you don't need to worry
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* // about method context.
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* properties: {
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* hello: {
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* get: function() {
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* return this._hello
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* },
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* set: function(value) {
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* this._hello = value
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* this._button.textContent = value
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* }
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* }
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* },
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*
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* // Set up methods that you can call from anywhere else in the configuration.
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* // Methods will be automatically bound to the correct value of `@`, so you
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* // don't need to worry about method context.
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* methods: {
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* _onDocClick: function() {
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* alert('document clicked')
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* },
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* _onButtonClick: function() {
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* alert('clicked on ' + this._hello + ' button')
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* }
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* }
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* })
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*/
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exports.create = function create(config) {
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if (customElements.get(config.tagName)) {
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throw Error('Custom element with tag name ' + config.tagName + ' already exists.')
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}
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var observedAttributes = config.observedAttributes || []
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var methods = config.methods || {}
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var properties = config.properties || {}
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var initialize = config.initialize || noOp
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var onConnect = config.onConnect || noOp
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var onDisconnect = config.onDisconnect || noOp
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var onAttributeChange = config.onAttributeChange || noOp
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var Class = makeClass()
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for (var key in methods) {
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if (!methods.hasOwnProperty(key)) continue
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Class.prototype[key] = methods[key]
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}
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Object.defineProperties(Class.prototype, properties)
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Class.prototype.connectedCallback = onConnect
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Class.prototype.disconnectedCallback = onDisconnect
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Class.prototype.attributeChangedCallback = onAttributeChange
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if (Array.isArray(observedAttributes)) {
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Object.defineProperty(Class, 'observedAttributes', {
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get: function () { return observedAttributes }
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})
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}
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Class.displayName = '<' + config.tagName + '> custom element'
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customElements.define(config.tagName, Class)
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}
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/**
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* Attempt to make an ES6 class using the Function constructor rather than
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* ordinary class syntax. The string we pass to the Function constructor is
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* static so there is no script injection risk. It allows us to catch
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* syntax errors at runtime for older browsers that don't support class and
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* fall back to an ES5 constructor function.
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*/
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function makeMakeClass() {
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try {
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return new Function([
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"return class extends HTMLElement {",
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" constructor() {",
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" super()",
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" for (var key in this) {",
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" var value = this[key]",
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" if (typeof value !== 'function') continue",
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" this[key] = value.bind(this)",
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" }",
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" }",
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"}",
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].join("\n"))
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} catch (e) {
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return function () {
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function Class() {
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// This is the best we can do to trick modern browsers into thinking this
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// is a real, legitimate class constructor and not a plane old JS function.
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var _this = HTMLElement.call(this) || this
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for (var key in _this) {
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var value = _this[key]
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if (typeof value !== 'function') continue
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_this[key] = value.bind(_this)
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}
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return _this
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}
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Class.prototype = Object.create(HTMLElement.prototype)
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Class.prototype.constructor = Class
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return Class
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}
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}
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}
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/**
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* Return a function for making an event based on what the browser supports.
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* IE11 doesn't support Event constructor, and uses the old Java-style
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* methods instead
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*/
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function makeMakeEvent() {
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try {
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// if calling Event with new works, do it that way
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var testEvent = new CustomEvent('myEvent', { detail: 1 })
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return function makeEventNewStyle(type, detail) {
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return new CustomEvent(type, { detail: detail })
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}
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} catch (_error) {
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// if calling CustomEvent with new throws an error, do it the old way
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return function makeEventOldStyle(type, detail) {
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var event = document.createEvent('CustomEvent')
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event.initCustomEvent(type, false, false, detail)
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return event
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}
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}
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}
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