Optional argument- alias if not there

argument-alias.js

//products is your array to crawl, if crawlEmitter is passed, it's used (for broadcasting via socket to frontend).  
//If not, it's aliased to console.log so the code with the logic stays the same (everything calls "crawlEmitter.emit").

async function run(products, crawlEmitter) {
    if(!crawlEmitter) {
        crawlEmitter = {
            emit: function() {
                console.log.apply(null, Array.from(arguments));
            }
        }
    }

    async function crawlPage(url) {
        const page = await browser.newPage();
        const pageResult = await page.goto(url);
        let resultObj = { success: pageResult.ok, url };
        resultGroup.push(resultObj);
        crawlEmitter.emit('crawled', resultObj);
        return page.close();
    }
    
    //more logic...
}

run(myProducts); //cli version
run(myProducts, crawlEmitter); //dashboard-UI version