// Retrieve params via url.search, passed into ctor
var url = new URL('https://example.com?foo=1&bar=2');
var params = new URLSearchParams(url.search);

// Pass in a string literal
var params2 = new URLSearchParams("foo=1&bar=2");
var params2a = new URLSearchParams("?foo=1&bar=2");

// Pass in a sequence of pairs
var params3 = new URLSearchParams([["foo", "1"], ["bar", "2"]]);

// Pass in a record
var params4 = new URLSearchParams({"foo": "1", "bar": "2"});