URL composition related

URL.searchParams

https://developer.mozilla.org/en-US/docs/Web/API/URL
https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams
https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
https://developers.google.com/web/updates/2016/01/urlsearchparams?hl=en

var url = new URL(location.hash.replace(/^#/,''), location.origin);

url.searchParams.set('x',1234)
url.search
"?x=1234"
// multiple x
url.searchParams.append('x',567)
// new y
url.searchParams.append('y',101)
url.search
"?x=1234&x=567&y=101"
// overwrite all the x entries:
url.searchParams.set('x',44)
url.search
"?x=44&y=101"
url.searchParams.delete('x')
url.search
"?y=101"
// direct assignment
url.search = 
"?x=1234&x=567&y=101"
url.search
"?x=1234&x=567&y=101"
Array.from(url.searchParams.keys())
(3) ["x", "x", "y"]
url.toString()
"http://localhost/things?x=1234&x=567&y=101"
location.hash = url.pathname + url.search
location.hash
"#/things?x=1234&x=567&y=101"
fetch(url.pathname, {
	method: 'POST',
	headers: new Headers({
		"Content-type": "application/x-www-form-urlencoded"
		//"application/json; charset=utf-8" "multipart/form-data" "application/x-www-form-urlencoded"
	}),
	// same format as GET url search params a&b&c
	body: url.searchParams
}).then((res)=>{ console.log(res); return res }).catch((res)=>{ console.warn(res); return res; });
// note automatic encoding of emoji and what typically is done via encodeURIComponent:
Object.entries({a:1,b:"🍻",c:'"stuff&things"'}).forEach(url.searchParams.set, url.searchParams);
url.search;
"?a=1&b=%F0%9F%8D%BB&c=%22stuff%26things%22"