javascript is not a quickbase thing, its a web standard. check out Mozilla Developer Network and W3Schools to learn about web languages. now i will give you a fast class on fetch:
fetch requires at least a url in position 1 and option init (initialise instructions)
example:
var url = "
https://yourquickbasedomain.quickbase.com/db/tableid?a=APIAddrecordetcetcetc";
var init = {
method: "POST",
credentials: "include",
headers: {
"Content-Type": "application/xml"
},
body: //put you body here
};
fetch(url, init).then(response => response.text()).then(str => (new DOMParser()).parseFromString(str, "text/xml")).then(function(xml) {
let rid = $("rid", xml).text()
console.log(rid);
})
