**Adding a parameter to the URL with JavaScript**
```
var url = new URL("http://foo.bar/?x=1&y=2");
// If your expected result is "http://foo.bar/?x=1&y=2&x=42"
url.searchParams.append('x', 42);
// If your expected result is "http://foo.bar/?x=42&y=2"
url.searchParams.set('x', 42);
```
https://stackoverflow.com/questions/486896/adding-a-parameter-to-the-url-with-javascript