Reverse-Engineering the Grammarly Affiliate API

gcheck.js

async function gcheck(text){
let f=new URLSearchParams()
f.set("aff_id","1122")
f.set("offer_id","41")
f.set("source","gc")
f.set("aff_sub","gceditor")
f.set("text",text)
return JSON.parse(atob(r=new URL((await (await fetch("https://irbis.grammarly.com/api/funnels/embedded/check", {"credentials":"omit","headers":{"accept":"*/*","accept-language":"en-US,en;q=0.9","content-type":"application/x-www-form-urlencoded; charset=UTF-8","sec-fetch-mode":"cors","sec-fetch-site":"cross-site"},"referrer":"https://www.grammarcheck.net/editor/","referrerPolicy":"no-referrer-when-downgrade","body":f.toString(),"method":"POST","mode":"cors"})).json()).reportUrl).searchParams.get("alerts")))
}

await gcheck(`stuffs and things go here!`)