@cycle/dom

Cycle DOM

A collection of Cycle.js drivers to enable interaction with the DOM. It includes a DOM Driver, an HTML Driver, both based on snabbdom as the Virtual DOM library.

npm install @cycle/dom

Browser support

These are the browsers we officially support currently. Cycle.js may not work (or work partially) in other browsers.

API

• makeDOMDriver
• makeHTMLDriver
• mockDOMSource
• h

makeDOMDriver(container, options)

A factory for the DOM driver function.

Takes a container to define the target on the existing DOM which this driver will operate on, and an options object as the second argument. The input to this driver is a stream of virtual DOM objects, or in other words, Snabbdom "VNode" objects. The output of this driver is a "DOMSource": a collection of Observables queried with the methods select() and events().

DOMSource.select(selector) returns a new DOMSource with scope restricted to the element(s) that matches the CSS selector given.

DOMSource.events(eventType, options) returns a stream of events of eventType happening on the elements that match the current DOMSource. The returned stream is an xstream Stream if you use @cycle/xstream-run to run your app with this driver, or it is an RxJS Observable if you use @cycle/rxjs-run, and so forth. The options parameter can have the field useCapture, which is by default false, except it is true for event types that do not bubble. Read more here https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener about the useCapture and its purpose.

DOMSource.elements() returns a stream of the DOM element(s) matched by the selectors in the DOMSource. Also, DOMSource.select(':root').elements() returns a stream of DOM element corresponding to the root (or container) of the app on the DOM.

Arguments:

• container: String|HTMLElement the DOM selector for the element (or the element itself) to contain the rendering of the VTrees.
• options: DOMDriverOptions an object with two optional fields: transposition: boolean enables/disables transposition of inner streams in the virtual DOM tree, modules: array contains additional Snabbdom modules.

Return:

(Function) the DOM driver function. The function expects a stream of of VNode as input, and outputs the DOMSource object.

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makeHTMLDriver(effect, options)

A factory for the HTML driver function.

Takes an effect callback function and an options object as arguments. The input to this driver is a stream of virtual DOM objects, or in other words, Snabbdom "VNode" objects. The output of this driver is a "DOMSource": a collection of Observables queried with the methods select() and events().

The HTML Driver is supplementary to the DOM Driver. Instead of producing elements on the DOM, it generates HTML as strings and does a side effect on those HTML strings. That side effect is described by the effect callback function. So, if you want to use the HTML Driver on the server-side to render your application as HTML and send as a response (which is the typical use case for the HTML Driver), you need to pass something like the html => response.send(html) function as the effect argument. This way, the driver knows what side effect to cause based on the HTML string it just rendered.

The HTML driver is useful only for that side effect in the effect callback. It can be considered a sink-only driver. However, in order to serve as a transparent replacement to the DOM Driver when rendering from the server, the HTML driver returns a source object that behaves just like the DOMSource. This helps reuse the same application that is written for the DOM Driver. This fake DOMSource returns empty streams when you query it, because there are no user events on the server.

DOMSource.select(selector) returns a new DOMSource with scope restricted to the element(s) that matches the CSS selector given.

DOMSource.events(eventType, options) returns an empty stream. The returned stream is an xstream Stream if you use @cycle/xstream-run to run your app with this driver, or it is an RxJS Observable if you use @cycle/rxjs-run, and so forth.

DOMSource.elements() returns the stream of HTML string rendered from your sink virtual DOM stream.

Arguments:

• effect: Function a callback function that takes a string of rendered HTML as input and should run a side effect, returning nothing.
• options: HTMLDriverOptions an object with one optional field: transposition: boolean enables/disables transposition of inner streams in the virtual DOM tree.

Return:

(Function) the HTML driver function. The function expects a stream of of VNode as input, and outputs the DOMSource object.

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mockDOMSource(mockConfig)

A factory function to create mocked DOMSource objects, for testing purposes.

Takes a streamAdapter and a mockConfig object as arguments, and returns a DOMSource that can be given to any Cycle.js app that expects a DOMSource in the sources, for testing.

The streamAdapter parameter is a package such as @cycle/xstream-adapter, @cycle/rxjs-adapter, etc. Import it as import a from '@cycle/rx-adapter, then provide it to mockDOMSource. This is important so the DOMSource created knows which stream library should it use to export its streams when you call DOMSource.events()` for instance.

The mockConfig parameter is an object specifying selectors, eventTypes and their streams. Example:

const domSource = mockDOMSource(RxAdapter, {
  '.foo': {
    'click': Rx.Observable.of({target: {}}),
    'mouseover': Rx.Observable.of({target: {}}),
  },
  '.bar': {
    'scroll': Rx.Observable.of({target: {}}),
    elements: Rx.Observable.of({tagName: 'div'}),
  }
});

// Usage
const click$ = domSource.select('.foo').events('click');
const element$ = domSource.select('.bar').elements();

The mocked DOM Source supports isolation. It has the functions isolateSink and isolateSource attached to it, and performs simple isolation using classNames. isolateSink with scope foo will append the class ___foo to the stream of virtual DOM nodes, and isolateSource with scope foo will perform a conventional mockedDOMSource.select('.__foo') call.

Arguments:

• mockConfig: Object an object where keys are selector strings and values are objects. Those nested objects have eventType strings as keys and values are streams you created.

Return:

(Object) fake DOM source object, with an API containing select() and events() and elements() which can be used just like the DOM Driver's DOMSource.

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h()

The hyperscript function h() is a function to create virtual DOM objects, also known as VNodes. Call

h('div.myClass', {style: {color: 'red'}}, [])

to create a VNode that represents a DIV element with className myClass, styled with red color, and no children because the [] array was passed. The API is h(tagOrSelector, optionalData, optionalChildrenOrText).

However, usually you should use "hyperscript helpers", which are shortcut functions based on hyperscript. There is one hyperscript helper function for each DOM tagName, such as h1(), h2(), div(), span(), label(), input(). For instance, the previous example could have been written as:

div('.myClass', {style: {color: 'red'}}, [])

There are also SVG helper functions, which apply the appropriate SVG namespace to the resulting elements. svg() function creates the top-most SVG element, and svg.g, svg.polygon, svg.circle, svg.path are for SVG-specific child elements. Example:

svg({width: 150, height: 150}, [
  svg.polygon({
    attrs: {
      class: 'triangle',
      points: '20 0 20 150 150 20'
    }
  })
])

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