markup-as-js v1.2.1

Markup As JS

A tiny, no-dependency library that provides simple functions for creating DOM nodes. Inspired by Flutter's "UI as Code" initiative.

Installation

npm install --save markup-as-js

Example Usage

import { div, p, b } from 'markup-as-js';

let el = div(
  {class: "foobar"}, //This is a set of key-value pairs representing the attributes of this node
  p(
    "I ", //String children are automatically converted to TextNodes
    b(
      "really"
    ), 
    " like cheese 🧀"
  )
);

console.log(el);

The above snippet creates an HTMLElement containing the following:

<div class="foobar"><p>I <b>really</b> like cheese 🧀</p></div>

Observables and Thenables

Observables (things that implement .subscribe()) and Thenables (things that implement .then(), like ES6 Promises) can be passed as node children or attribute values.

When the value is updated (for observables) or resolves (for thenables), the DOM node or attribute that the observable was passed to will be updated. This facilitates reactive programming. For example:

const counter = new SimpleObservable(0);
const isTen = new SimpleObservable(false);
counter.subscribe(v => isTen.set(v === 10));

return div(
  p(
    counter,
  ),
  button(
    {
      onclick: () => counter.set(counter.value + 1),
      disabled: isTen,
    },
    "Increment"
  ),
  new Promise(resolve => setTimeout(() => resolve("This text node shows up after five seconds"), 5000))
);

(SimpleObservable is a class provided by this library that is, unsurprisingly, a simple observable. It has subscribe and set methods and a value property, and the constructor takes the initial value.)

Important Note: If you ever discard a node that was passed an observable without also discarding the Observable (including unsubscribing it from any observables it is subscribed to), you must call .teardown() on the discarded node. Otherwise, the observable will still have a reference to the discarded node and it will not be garbage-collected, causing a memory leak.