How to serialize an Object into a list of URL query parameters?

Without knowing the keys of a JavaScript Object, how can I turn something like...

var obj = {
   param1: 'something',
   param2: 'somethingelse',
   param3: 'another'
}

obj[param4] = 'yetanother';

...into...

var str = 'param1=something&param2=somethingelse&param3=another&param4=yetanother';

...?

One line with no dependencies:

new URLSearchParams(obj).toString();
// OUT: param1=something&param2=somethingelse&param3=another&param4=yetanother

Use it with the URL builtin like so:

let obj = { param1: 'something', param2: 'somethingelse', param3: 'another' }
obj['param4'] = 'yetanother';
const url = new URL(`your_url.com`);
url.search = new URLSearchParams(obj);
const response = await fetch(url);

[Edit April 4, 2020]: null values will be interpreted as the string 'null'.

If you use jQuery, this is what it uses for parameterizing the options of a GET XHR request:

$.param( obj )

http://api.jquery.com/jQuery.param/