Example of using a CORS proxy to fetch data from a website.

cat_api.js

const data = new FormData();
// I don't know what these values should be...
data.set('txtIDnummer', '123#567');
data.set('txtChipNr', '');
data.set('ddlLan', '');
data.set('txtOrt', '');
data.set('ddlKon', '');

// Send a post request
const request = await fetch('https://corsproxy.io/?' + encodeURIComponent('https://hundar.skk.se/agarreg/katt_sok.aspx'), {
	method: 'POST',
	headers: {
		// Sometimes APIs let you request data in a specific format, though I don't think this page supports that.
		// accept: 'text/JSON'
	},
	body: data,
});
console.log(request);
if (!request.ok) throw new Error(`uh oh ${request.statusText}`, { cause: request });

// Parse the response HTML page into a document:
const html_text = await request.text();
const doc = new DOMParser().parseFromString(html_text, 'text/html');
console.log(doc);

// Pull the response rows out of that document:
// TODO: Use a CSS selector that pulls out the HTML elements containing the returned results.
const results = Array.from(doc.body.querySelectorAll("tr"), el => el.innerHTML);
console.log(results);