Critical errors on global.js script in old browser (<=2021) caused by # usage for private fields on SectionId class

[uPesyLabs]

Describe the current behavior

On old browser, there is an error in global.js that prevent the script to be loaded successfully.

Since it's a critical JS, with some functions used by other scripts, some other webcomponents doesn't work either.

Describe the expected behavior

No error when loading the global.js script.

Version information (Dawn, browsers and operating systems)

• Dawn Version: 15.0.1
• iOS, v14.1 / Chrome Mobile 92.0.4515.90

Possible solution

Apparently it's caused by this new Class :

dawn/assets/global.js

Lines 9 to 26 in a22f8de

	class SectionId {
	static #separator = '__';
	// for a qualified section id (e.g. 'template--22224696705326__main'), return just the section id (e.g. 'template--22224696705326')
	static parseId(qualifiedSectionId) {
	return qualifiedSectionId.split(SectionId.#separator)[0];
	}
	// for a qualified section id (e.g. 'template--22224696705326__main'), return just the section name (e.g. 'main')
	static parseSectionName(qualifiedSectionId) {
	return qualifiedSectionId.split(SectionId.#separator)[1];
	}
	// for a section id (e.g. 'template--22224696705326') and a section name (e.g. 'recommended-products'), return a qualified section id (e.g. 'template--22224696705326__recommended-products')
	static getIdForSection(sectionId, sectionName) {
	return `${sectionId}${SectionId.#separator}${sectionName}`;
	}
	}

The fix is : Don't use this new feature of private field with #. Can be hardcoded directly or use a const instead.
You can check the browser compatibility here : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Private_properties#browser_compatibility

Additional context/screenshots

On Chrome Mobile 92.0.4515.90 on iPhone 12 (from Browserstack)