I found DOMParser in react-scan source code as shown below.

const iconSprite = new DOMParser().parseFromString(
    ICONS,
    'image/svg+xml',
  ).documentElement;

This picked from line 54 in packages/scan/src/core/index.ts. In this article, we understand

• What is DOMParser?

• How it is used in react-scan?

What is DOMParser?

The DOMParser interface provides the ability to parse XML or HTML source code from a string into a DOM Document.

You can perform the opposite operation — converting a DOM tree into XML or HTML source — using the XMLSerializer interface.

In the case of an HTML document, you can also replace portions of the DOM with new DOM trees built from HTML by setting the value of the Element.innerHTML and outerHTML properties. These properties can also be read to fetch HTML fragments corresponding to the corresponding DOM subtree.

Note that XMLHttpRequest can parse XML and HTML directly from a URL-addressable resource, returning a Document in its response property.

Read more about DOMParser.

How it is used in react-scan?

DOMParser is used in a function called initRootContainer.

const initRootContainer = (): RootContainer => {
  ...
  const fragment = document.createDocumentFragment();
  const cssStyles = document.createElement('style');
  cssStyles.textContent = styles;
 
  const iconSprite = new DOMParser().parseFromString(
    ICONS,
    'image/svg+xml',
  ).documentElement;
 
  fragment.appendChild(iconSprite);
  ...
  return { rootContainer, shadowRoot };
};

iconSprite is assigned a value returned by DOMParser.documentElement. parseFromString accepts ICONS that is imported from packages/scan/src/web/assets/svgs/svgs.ts.

Now then, this svgs.ts has ICONS variable that contains svg as string as shown below

export const ICONS = `
<svg xmlns="http://www.w3.org/2000/svg" style="display: none;">
  <symbol id="icon-inspect" viewBox="0 0 24 24" fill="none" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
    <path d="M12.034 12.681a.498.498 0 0 1 .647-.647l9 3.5a.5.5 0 0 1-.033.943l-3.444 1.068a1 1 0 0 0-.66.66l-1.067 3.443a.5.5 0 0 1-.943.033z"/>
    <path d="M5 3a2 2 0 0 0-2 2"/>
    <path d="M19 3a2 2 0 0 1 2 2"/>
    ...

This below code snippet converts to:

new DOMParser().parseFromString(
  ICONS,
  'image/svg+xml',
)

This string is converted into a DOM document hence you have .documentElement that is assigned to iconSprite.

About me:

Hey, my name is Ramu Narasinga. I study large open-source projects and create content about their codebase architecture and best practices, sharing it through articles, videos.

I am open to work on interesting projects. Send me an email at ramu.narasinga@gmail.com

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References:

1. https://developer.mozilla.org/en-US/docs/Web/API/DOMParser

2. https://github.com/aidenybai/react-scan/blob/main/packages/scan/src/core/index.ts#L54