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shadow-dom-selector
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4.1.2 • Public • Published

shadow-dom-selector

A very small JavaScript utility to query DOM elements through the Shadow DOM subtrees in a sync or an async way.

Deployment Status   Coverage Status   npm version

Introduction

Having a DOM tree formed of Shadow DOM subtrees like the next one:

<body>
  <section>
    #shadow-root (open)
      <h1>Title</h1>
      <article>
        #shadow-root (open)
          <h2>Subtitle</h2>
          <ul>
            <li>Item 1</li>
            <li>Item 2</li>
            <li>Item 1</li>
          </ul>
      </article>
  </section>
</body>

If one wants to query for the li elements, it is required to do this:

const firstLi = document.querySelector('section').shadowRoot.querySelector('article').shadowRoot.querySelector('ul > li');

const allLis = document.querySelector('section').shadowRoot.querySelector('article').shadowRoot.querySelectorAll('ul > li');

const shadow = document.querySelector('section').shadowRoot.querySelector('article').shadowRoot;

shadow-dom-selector allows you to do the same in the next way:

// $ character at the end of a selector means to select its Shadom DOM

import {
  querySelector,
  querySelectorAll,
  shadowRootQuerySelector,
  deepQuerySelector,
  deepQuerySelectorAll
} from 'shadow-dom-selector';

const firstLi = querySelector('section$ article$ ul > li');
const allLis = querySelectorAll('section$ article$ ul > li');
const shadow = shadowRootQuerySelector('section$ article$');

const deepFirstLi = deepQuerySelector('li');
const deepAllLi = deepQuerySelectorAll('li');

It will traverse all the Shadow DOM subtrees removing all the hassle of writing long concatenated queries.

It checks for the existence of elements

With the same previous DOM tree, if we do this:

const element = document.querySelector('article').shadowRoot.querySelector('div').shadowRoot.querySelector('section > h1');

It will throw an error, because none of the elements in those queries exist. If you don‘t know if the elements exist or not, you will require to wrap all the code in conditions or use optional chaining if your target is ES2015 or greater:

// With conditions
const article = document.querySelector('article');
if (article) {
  const articleShadowRoot = article.shadowRoot;
  if (articleShadowRoot) {
    const div = articleShadowRoot.querySelector('div');
    if (div) {
      const shadow = div.shadowRoot;
      if (shadow) {
        const element = shadow.querySelector('section > h1');
        const elements = shadow.querySelectorAll('p');
      }
    }
  }
}

// With optional chaining in ES2015+
const shadow = document.querySelector('article')?.shadowRoot?.querySelector('div')?.shadowRoot;
const element = document.querySelector('article')?.shadowRoot?.querySelector('div')?.shadowRoot?.querySelector('section > h1');
const elements = document.querySelector('article')?.shadowRoot?.querySelector('div')?.shadowRoot?.querySelectorAll('p');

Which will return undefined if some element doesn‘t exist. With shadow-dom-selector, you just need to write the query and it will return the same that is returned by the native querySelector and querySelectorAll if the query cannot be satisfied.

import {
  querySelector,
  querySelectorAll,
  shadowRootQuerySelector,
  deepQuerySelector,
  deepQuerySelectorAll
} from 'shadow-dom-selector';

const shadow = shadowRootQuerySelector('article$ div$'); // null
const element = querySelector('article$ div$ section > h1'); // null
const elements = querySelectorAll('article$ div$ p'); // empty NodeList
const deepElement = deepQuerySelector('span') // null;
const deepElements = deepQuerySelectorAll('p'); // empty NodeList

Async queries

If the elements are not already rendered into the DOM in the moment that the query is made you will receive null. shadow-dom-selector allows you to wait for the elements to appear deciding how many times it will try to query for the element before giving up and returning null or an empty NodeList.

// Using the async methods
import {
  asyncQuerySelector,
  asyncQuerySelectorAll,
  asyncShadowRootQuerySelector,
  asyncDeepQuerySelector,
  asyncDeepQuerySelectorAll
} from 'shadow-dom-selector';

asyncShadowRootQuerySelector('article$ div$')
  .then((shadowRoot) => {
      // Do stuff with the shadowRoot
      // If it is not found after all the retries, it will return null
  });

asyncQuerySelector('article$ div$ section > h1')
  .then((h1) => {
      // Do stuff with the h1 element
      // If it is not found after all the retries, it will return null
  });

asyncQuerySelectorAll('article$ div$ p')
  .then((paragraphs) => {
      // Do stuff with the paragraphs
      // If they are not found after all the retries, it will return an empty NodeList
  });

asyncDeepQuerySelector('h1')
  .then((h1) => {
      // Do stuff with the h1 element
      // If it is not found after all the retries, it will return null
  });

asyncDeepQuerySelectorAll('p')
  .then((paragraphs) => {
      // Do stuff with the paragraphs
      // If they are not found after all the retries, it will return an empty NodeList
  });

// Using de AsyncSelector class
import { AsyncSelector } from 'shadow-dom-selector';

const selector = new AsyncSelector();

selector.query('article').$.query('div').$.element
  .then((shadowRoot) => {
    // Do stuff with the shadowRoot
    // If it is not found after all the retries, it will return null
  });

selector.query('article').$.query('div').$.query('section > h1').element
  .then((h1) => {
    // Do stuff with the h1 element
    // If it is not found after all the retries, it will return null
  });

selector.query('article').$.query('div').$.query('p').all
  .then((paragraphs) => {
    // Do stuff with the paragraphs
    // If they are not found after all the retries, it will return an empty NodeList
  });

selector.deepQuery('h1').element
  .then((h1) => {
    // Do stuff with the h1 element
    // If it is not found after all the retries, it will return null
  });

selector.deepQuery('p').all
  .then((paragraphs) => {
    // Do stuff with the paragraphs
    // If they are not found after all the retries, it will return an empty NodeList
  });

Either the async methods or the async dot notation allow you to to specify the amount of retries and the delay between each one of them. Consult the API section for more details.

Install

npm

npm install shadow-dom-selector

yarn

yarn add shadow-dom-selector

PNPM

pnpm add shadow-dom-selector

In the browser

It is possible to include a compiled version of the package directly in an HTML file. It will create a global ShadowDomSelector object containing all the exported functions that can be accessed from anywhere in your JavaScript code.

  1. Copy the JavaScript file index.js, located in the root of the dist/ folder
  2. Put it in the folder that you prefer in your web server
  3. Include it in your HTML file
<script src="wherever/you/want/to/place/index.js"></script>
/* There will be a global variable named ShadowDomSelector containing all the functions */
ShadowDomSelector.querySelector;
ShadowDomSelector.deepQuerySelector;
ShadowDomSelector.querySelectorAll;
ShadowDomSelector.deepQuerySelectorAll;
ShadowDomSelector.shadowRootQuerySelector;
ShadowDomSelector.asyncQuerySelector;
ShadowDomSelector.asyncDeepQuerySelector;
ShadowDomSelector.asyncQuerySelectorAll;
ShadowDomSelector.asyncDeepQuerySelectorAll;
ShadowDomSelector.asyncShadowRootQuerySelector;
ShadowDomSelector.AsyncSelector;

API

querySelector

Performs a query selection passing through the shadowRoot of elements if you add $ after them.

querySelector(selectors): Element | null;
querySelector(root, selectors): Element | null;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document

deepQuerySelector

Performs a query selection of an element searching for it recursively in the whole DOM tree even if it needs to pass through the shadowRoots of elements.

Note: use this method carefully, depending on the extension of your DOM tree, it could be an expensive task in terms of resources. Do this when you need to query for an element that could appear in any part of the DOM tree so you don‘t know its exact position, otherwise, the querySelector method is recommended.

deepQuerySelector(selectors): Element | null;
deepQuerySelector(root, selectors): Element | null;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document

querySelectorAll

Performs a querySelectionAll query passing through the shadowRoot of elements if you add $ after them.

querySelectorAll(selectors): NodeListOf<Element>;
querySelectorAll(root, selectors): NodeListOf<Element>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document

deepQuerySelectorAll

Performs a querySelectionAll query of elements searching for them recursively in the whole DOM tree even if it needs to pass through the shadowRoots of elements.

Note: use this method carefully, depending on the extension of your DOM tree, it could be an expensive task in terms of resources. Do this when you need to query for elements that could appear in any part of the DOM tree so you don‘t know their exact position, otherwise, the querySelectionAll method is recommended.

deepQuerySelectorAll(selectors): NodeListOf<Element>;
deepQuerySelectorAll(root, selectors): NodeListOf<Element>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document

shadowRootQuerySelector

Performs a query selection of a shadowRoot passing through the shadowRoot of elements if you add $ after them.

shadowRootQuerySelector(selectors): ShadowRoot | null;
shadowRootQuerySelector(root, selectors): ShadowRoot | null;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors must end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document

asyncQuerySelector

Performs an asynchronous query selection passing through the shadowRoot of elements if you add $ after them.

asyncQuerySelector(selectors): Promise<Element | null>;
asyncQuerySelector(root, selectors): Promise<Element | null>;
asyncQuerySelector(selectors, asyncParams): Promise<Element | null>;
asyncQuerySelector(root, selectors, asyncParams): Promise<Element | null>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

asyncDeepQuerySelector

Performs an asynchronous query selection of an element searching for it recursively in the whole DOM tree even if it needs to pass through the shadowRoots of elements.

Note: use this method carefully, depending on the extension of your DOM tree, it could be an expensive task in terms of resources. Do this when you need to query for an element that could appear in any part of the DOM tree so you don‘t know its exact position, otherwise, the asyncQuerySelector method is recommended.

asyncDeepQuerySelector(selectors): Promise<Element | null>;
asyncDeepQuerySelector(root, selectors): Promise<Element | null>;
asyncDeepQuerySelector(selectors, asyncParams): Promise<Element | null>;
asyncDeepQuerySelector(root, selectors, asyncParams): Promise<Element | null>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

asyncQuerySelectorAll

Performs an asynchronous querySelectionAll query passing through the shadowRoot of elements if you add $ after them.

asyncQuerySelectorAll(selectors): Promise<NodeListOf<Element>>;
asyncQuerySelectorAll(root, selectors): Promise<NodeListOf<Element>>;
asyncQuerySelectorAll(selectors, asyncParams): Promise<NodeListOf<Element>>;
asyncQuerySelectorAll(root, selectors, asyncParams): Promise<NodeListOf<Element>>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

asyncDeepQuerySelectorAll

Performs an asynchronous querySelectionAll query of elements searching for them recursively in the whole DOM tree even if it needs to pass through the shadowRoots of elements.

Note: use this method carefully, depending on the extension of your DOM tree, it could be an expensive task in terms of resources. Do this when you need to query for elements that could appear in any part of the DOM tree so you don‘t know their exact position, otherwise, the asyncQuerySelectorAll method is recommended.

asyncDeepQuerySelectorAll(selectors): Promise<NodeListOf<Element>>;
asyncDeepQuerySelectorAll(root, selectors): Promise<NodeListOf<Element>>;
asyncDeepQuerySelectorAll(selectors, asyncParams): Promise<NodeListOf<Element>>;
asyncDeepQuerySelectorAll(root, selectors, asyncParams): Promise<NodeListOf<Element>>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors may not end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

asyncShadowRootQuerySelector

Performs an asynchronous query selection of a shadowRoot passing through the shadowRoot of elements if you add $ after them.

asyncShadowRootQuerySelector(selectors): Promise<ShadowRoot | null>;
asyncShadowRootQuerySelector(root, selectors): Promise<ShadowRoot | null>;
asyncShadowRootQuerySelector(selectors, asyncParams): Promise<ShadowRoot | null>;
asyncShadowRootQuerySelector(root, selectors, asyncParams): Promise<ShadowRoot | null>;
Parameter Optional Description
selectors no A string containing one or more selectors to match. Selectors must end in a Shadow DOM ($)
root yes The element from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

AsyncSelector class

This class creates an instance of an element that could be used to perform asynchronous query selections in the DOM tree passing through the shadowRoot of elements.

new AsyncSelector();
new AsyncSelector(root);
new AsyncSelector(root, asyncParams);
Parameter Optional Description
root yes The element or shadowRoot from where the query should be performed, it defaults to document
asyncParams yes An object containing the parameters which control the retries 
// asyncParams properties
{
  retries?: number; // how many retries before giving up (defaults to 10)
  delay?: number; // delay between each retry (defaults to 10)
}

The instances of this class have the next properties:

Property Type Description
element Promise<Element | ShadowRoot | null> A promise that resolves in the queried element
all Promise<NodeListOf<Element>> A promise that resolves in a Nodelist with all queried elements
$ Promise<ShadowRoot | null> A promise that resolves in the shadowRoot of the queried element
asyncParams Same asyncParams previously shown An object containing the parameters which control the retries

And the next methods:

Method Return Description
eq(index: number) Promise<Element | null> Returns a promise that resolves in the element in the index position of the queried elements (startig from 0)
query(selector: string) AsyncSelector Performs a query and returns a new AsyncSelector instance
deepQuery(selector: string) AsyncSelector Performs a deep query (even through elements' shadowRoot) ans returns a new AsyncSelector instance
Examples of the AsyncSelector class
const selector = new AsyncSelector(); // Starting to query in the document with the default asyncParams
await selector.element === document;
await selector.all; // Empty Node list
await selector.$; // null
await selector.eq(0); // null
const selector = AsyncSelector({
  retries: 100,
  delay: 50
}); // Starting to query in the document with custom asyncParams
await selector.query('section').$.element === document.querySelector('section').shadowRoot;
await selector.query('section').$.all; // Empty Node list
await selector.query('section').$.query('article').all === document.querySelector('section').shadowRoot.querySelectorAll('article');
await selector.query('section').$.query('ul li').eq(1) === document.querySelector('section').shadowRoot.querySelectorAll('ul li')[1];
await selector.deepQuery('li.delayed-li').element; // try to query the element deep in the shadowDOM tree until the retries/delay expire
await selector.deepQuery('li.delayed-li').all; // try to perform a querySelectorAll deep in the shadowDOM tree until the retries/delay expire
selector.query('section').$.query('article').asyncParams; // { retries: 100, delay: 50 }

Readme

Keywords

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Install

npm i shadow-dom-selector

Repository

github.com/elchininet/shadow-dom-selector

Homepage

github.com/elchininet/shadow-dom-selector#readme

Weekly Downloads

31

Version

4.1.2

License

Apache-2.0

Unpacked Size

65.2 kB

Total Files

7

Last publish

Collaborators

  • elchininet
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