let needUpdateBrowser = (()=>{
	try {
		return !Boolean(eval("undefined?.undefined ?? true"));
	} catch (e) {
		if (e.name !== 'SyntaxError') throw e // Throw the error if it is not a SyntaxError
		return true;
	}
})();

if (needUpdateBrowser)
{
	let browserVersion = ((UA)=>{
		let regRes;
		if (regRes = /\b(Firefox|Chrome)\/([\d\.]+)/ig.exec(UA))
		{
			return `${regRes[1]} ${regRes[2]}`;
		}else if (regRes = /\bVersion\/([\d\.]+)\s+.*\b(Safari)\//ig.exec(UA))
		{
			return `${regRes[2]} ${regRes[1]}`;
		}else
		{
			UA;
		}
	})(navigator.userAgent);

	let alertStr;
	if (/^zh-(?:han(?:s|t)-)?/.test(navigator.language)) {
		alertStr = 
`🙁浏览器内核版本太老
您的浏览器版本为:
${browserVersion}

您的浏览器不支持本程序使用的 可选链操作符(?.) 和 空值合并操作符(??)。

请更新您的浏览器到 Firefox(火狐) ≥ 74 或 Chrome(谷歌) ≥ 80 或 Safari(苹果) ≥ 13.1。`;
	} else {
		alertStr = 
`🙁Browser kernel is too old
Your browser is:
${browserVersion}

Your browser does not support Optional chaining (?.) and Nullish coalescing operator (??) used in this program.

Please update your browser to Firefox ≥ 74 or Chrome ≥ 80 or Safari ≥ 13.1.`;
	}

alert(alertStr);
document.write(alertStr.replace(/\n/g,'<br />'));
}