get_critical.js

const critical = require('critical');

function generateCCSS(inputURL) {
	const is_mobile = false;

	var ccss_options = {
		src: inputURL,
		ignore: {
			atrule: ['@font-face', '@import'],
		},		
		minify: false,
	};

	ccss_options.userAgent = 'Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1';

	ccss_options.width = is_mobile ? 479 : 1366;
	ccss_options.height = is_mobile ? 812 : 768;

	try {
		critical.generate(ccss_options).then(criticalCss => {
			console.log(criticalCss.css);
			console.log('success')
		}).catch(err => {
			console.log('err1', err);
		});
	} catch (err) {
		console.log('err2', err);
	}
}

const inputURL = process.argv[2];
generateCCSS(inputURL);