DNA

Progressive Web Components.

Manipulating the DOM

Why and how

Since DNA does not require any Custom Elements polyfill, the life cycle is delegated to the render cycle which uses the DOM helper under the hood. This helper invokes the life cycle methods for each DOM operation like appendChild, removeChild etc. If you want to manipulate the DOM tree outside of a render cycle, always use DOM methods instead of the HTMLElement prototype:

import { ChildComponent } from './child-component';

const child = new ChildComponent();

// ✘ DON'T
document.body.appendChild(child);
// ✔︎ DO!
DOM.appendChild(document.body, child);

All methods inherit the prototype signature with the context node as first argument:

`HTMLElement.prototype`	`DOM` helper
`appendChild(newChild)`	`appendChild(parent, newChild)`
`removeChild(oldChild)`	`removeChild(parent, oldChild)`
`insertBefore(newChild, refChild)`	`insertBefore(parent, newChild, refChild)`
`replaceChild(newChild, oldChild)`	`replaceChild(parent, newChild, oldChild)`
`getAttribute(qualifiedName)`	`getAttribute(element, qualifiedName)`
`hasAttribute(qualifiedName)`	`hasAttribute(element, qualifiedName)`
`setAttribute(qualifiedName, value)`	`setAttribute(element, qualifiedName, value)`
`removeAttribute(qualifiedName)`	`removeAttribute(element, qualifiedName)`
`dispatchEvent(event)`	`dispatchEvent(element, event)`
`matches(selector)`	`matches(element, selector)`

Please note that all DNA components already wrap those methods with the DOM helper, so if you are appending or removing children from a component you can directly use the prototyped appendChild and removeChild methods:

import { DOM } from '@chialab/dna';
import { ParentComponent } from './parent-component';
import { ChildComponent } from './child-component';

const parent = new ParentComponent();
const child = new ChildComponent();

// ✔︎ OK!
parent.appendChild(child);

Setting innerHTML

Since DNA render cycle is responsible for Custom Element's life cycle support in old browser, directly setting the innerHTML to an element can lead to unespected behavior. You should always consider to use the html helper coombine with the render method, but where it is not possible remember to invoke the customElements.upgrade method to the root of the change:

import { customElements } from '@chialab/dna';
import './video-player.js';

const element = document.querySelector('main');
element.innerHTML = `&lt;article>
    &lt;h1>Title&lt;/h1>
    &lt;video-player>
        &lt;source src="/video.mp4" />
    &lt;/video-player>
&lt;/article>`;

customElements.upgrade(element);

Integration with third party libraries

Sometimes you need to encapsulate in DNA another UI library, like Mapbox or Pickr. Since DNA components are DOM nodes, the integration is possible using the element context as library param:

import { Component, customElement } from '@chialab/dna';
import Pickr from '@simonwep/pickr';

@customElement('color-picker')
export class ColorPicker extends Component {
    private pickr: Pickr;

    connectedCallback() {
        super.connectedCallback();
        this.pickr = new Pickr({
            el: this,
        });
    }

    disconnectedCallback() {
        this.pickr.destroyAndRemove();
        super.disconnectedCallback();
    }
}