Someone recently asked over the phone for the pure JavaScript example of getting a set of point values through the API based on tags. The solution (currently) is to query the data points first, then compose a list to submit to the point-values endpoint, like,

var token = "Token auth!";
var baseUrl = 'http://localhost:8082/rest';
function newHttpRequest(method, url, headers) {
	var http = new XMLHttpRequest();
	http.open(method, url, true);
	
	http.setRequestHeader("Accept", "application/json")
	http.setRequestHeader("Authorization", "Bearer " + token)
	if(headers != null) {
		for(var header in headers)
			http.setRequestHeader(header, headers[header]);
	}
			
	return http;
}

valuesRequestBody = {
  "dateTimeFormat": "YYYY-MM-dd'T'HH:mm:ss.SSSZ",
  "fields": [
    "XID",
    "VALUE"
  ],
  "from": "2018-10-16T18:43:20.111Z",
  "limit": 1000,
  "timePeriod": {
    "periods": 1,
    "type": "HOURS"
  },
  "timezone": "America/Denver",
  "to": "2018-10-19T18:43:20.111Z",
  "truncate": true,
  "xids": [
  ]
}

getDataPoints = newHttpRequest('GET', baseUrl + '/v2/data-points?eq(tags.device,example)&limit(100)', null);
getDataPoints.onreadystatechange  = function() {
	if (getDataPoints.readyState == XMLHttpRequest.DONE) {
		var dataPoints = JSON.parse(this.responseText).items;
		var dpXids = []
		for(var k = 0; k < dataPoints.length; k+=1)
			dpXids.push(dataPoints[k].xid);
		valuesRequestBody.xids = dpXids;
		getPointValues.send(JSON.stringify(valuesRequestBody));
	}
}

getPointValues = newHttpRequest('POST', baseUrl + '/v2/point-values/multiple-arrays/time-period/ALL', {"Content-Type": "application/json"});
getPointValues.onreadystatechange  = function() {
	if (getPointValues.readyState == XMLHttpRequest.DONE) {
		//var response = JSON.parse(getPointValues.responseText); //Then do stuff
		console.log(getPointValues.responseText);
	}
}

getDataPoints.send(null);

This JavaScript will query the data points for up to 100 with the device tag 'example' and then request up to 1000 values for each (because it's a multiple arrays, single arrays the limit applies to all), where a 'value' in this context is a one hour rollup of ALL statistics options.