Ways of detecting webp browser support

test-lossy-webp-support.js

// works for all browsers
async function supportsWebp():Promise<boolean> {
	const img = new Image();
	return new Promise(resolve => {
		img.onload = function () {resolve((img.width > 0) && (img.height > 0));};
		img.onerror = function () {resolve(false);};
		img.src = "data:image/webp;base64," + "UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA";
	});
}

// doesn't work with Edge? Edge supports webp, but as self.createImageBitmap is not available, this functions returns false
async function supportsWebpOld():Promise<boolean> {
	if (!self.createImageBitmap) return false;
	const webpData = 'data:image/webp;base64,UklGRh4AAABXRUJQVlA4TBEAAAAvAAAAAAfQ//73v/+BiOh/AAA=';
	const blob = await fetch(webpData).then(r => r.blob());
	return createImageBitmap(blob).then(() => true, () => false);
}