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How get features from a style's layer in Mapbox GL JS?

I'm a learner of JavaScript and have a problem with Mapbox GL JS: I have a style in Mapbox Studio, where there is one my layer — "locations". I've added it as a tileset. There are two GeoJSON-points in this layer, but I can't get them in GL JS.
I've found that I should use method querySourceFeatures(sourceID, [parameters]), but I have problems with correct filling its parameters. I wrote:
var allFeatures = map.querySourceFeatures('_id-of-my-tyleset_', {
'sourceLayer': 'locations'
});
..and it doesn't work.
More interesting, that later in the code I use this layer with method queryRenderedFeatures, and it's okay:
map.on('click', function(e) {
var features = map.queryRenderedFeatures(e.point, {
layers: ['locations']
});
if (!features.length) {
return;
}
var feature = features[0];
flyToPoint(feature);
var popup = new mapboxgl.Popup({
offset: [0, -15]
})
.setLngLat(feature.geometry.coordinates)
.setHTML('<h3>' + feature.properties.name + '</h3>' + '<p>' +
feature.properties.description + '</p>')
.addTo(map);
});
I have read a lot about adding layers on a map and know that the answer is easy, but I can't realise the solution, so help, please :)
Here is the project on GitHub.

Your problem is that your map, like all maps created in Mapbox Studio by default, uses auto-compositing. You don't actually have a source called morganvolter.cj77n1jkq1ale33jw0g9haxc0-2haga, you have a source called composite with many sub layers.
You can find the list of layers like this:
map.getSource('composite').vectorLayerIds
Which reveals you have a vector layer called akkerman. ("locations" is the name of your style layer, not your source layer). Hence your query should be:
map.querySourceFeatures('composite', {
'sourceLayer': 'akkerman'
});
Which returns 4 features.

There are lots of questions about Mapbox get features after filter or Mapbox get features before filter. And I could see there are many posts are scattering around but none of them seem to have a FULL DETAILED solution. I spend some time and put both solution together under a function, try this in jsbin.
Here it is for someone interested:
function buildRenderedFeatures(map) {
// get source from a layer, `mapLayerId` == your layer id in Mapbox Studio
var compositeSource = map.getLayer(mapLayerId.toString()).source;
//console.log(map.getSource(compositeSource).vectorLayers);
var compositeVectorLayerLength = map.getSource(compositeSource).vectorLayers.length - 1;
//console.log(compositeVectorLayerLength);
// sourceId === tileset id which is known as vector layer id
var sourceId = map.getSource(compositeSource).vectorLayers[compositeVectorLayerLength].id;
//console.log(sourceId);
// get all applied filters if any, this will return an array
var appliedFilters = map.getFilter(mapLayerId.toString());
//console.log(appliedFilters);
// if you want to get all features with/without any filters
// remember if no filters applied it will show all features
// so having `filter` does not harm at all
//resultFeatures = map.querySourceFeatures(compositeSource, {sourceLayer: sourceId, filter: appliedFilters});
var resultFeatures = null;
// this fixes issues: queryRenderedFeatures getting previous features
// a timeout helps to get the updated features after filter is applied
// Mapbox documentation doesn't talk about this!
setTimeout(function() {
resultFeatures = map.queryRenderedFeatures({layers: [mapLayerId.toString()]});
//console.log(resultFeatures);
}, 500);
}
Then you call that function like: buildRenderedFeatures(map) passing the map object which you already have when you created the Mapbox map.
You will then have resultFeatures will return an object which can be iterated using for...in. You can test the querySourceFeatures() code which I commented out but left for if anyone needs it.

OpenLayers not letting me add Popup

So I have (or had) a working version of OpenStreetMaps, but now that I want to add popups onto the map, the whole thing breaks. This is the code pertaining to the issue of the popup. The crazy thing is that I copy and pasted the code from the official wiki in order to just get a working example.
function init() {
map = new OpenLayers.Map( 'heatmapArea');
var query = new OpenLayers.LonLat(-122.2928337167, 37.5549570333).transform(
new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());
var popup = new OpenLayers.Popup.FramedCloud("Popup", query, null, "Text", null, true);
map.addPopup(popup, false);
var lat = 39.3138895;
var lon = -98.2233523;
var zoom = 4;
var position = new OpenLayers.LonLat(lon, lat).transform( EPSG_WGS84, EPSG_900913);
map.setCenter(position, zoom );
}
The issue as it appears in my browser console is:
I have removed the code which I don't think is relevant to this issue but I could provide more if that is necessary. I have googled around extensively and all of the examples that I find work fine on the website I visit, but breaks my map and every StackOverflow answer to somebody else seems to work fine for the original poster, but once again, breaks my map.
Here's one of the website I tried to copy:
http://www.rigacci.org/openlayers/other_examples/markers.html
I am very eager to get this problem solved and any help would be greatly appreciated. Thanks!
-C.J.

Someone who really knows their way around the OL API will be able to explain this properly, but basically, your code is fine, but you need to reorder it. You need to add a map layer, and zoom to an extent, before you can call addPopup. I think this is because addPopup doesn't need an explicit layer of its own; it uses the map layer; and therefore you need a map layer on your map before trying to use it. That makes sense, but I am not sure why you need also to have called a zoom/zoomToExtent function.
Here's a fiddle, I've tried to leave your code as unchanged as possible:
http://jsfiddle.net/sifriday/u3j6h97d/3/
And here's the JS with some comments:
function init() {
var map = new OpenLayers.Map( 'heatmapArea');
// Add a map layer before trying to use addPopup
map.addLayer(new OpenLayers.Layer.OSM());
// Call the zoom function before trying to use addPopup
var lat = 39.3138895;
var lon = -98.2233523;
// I've changed the zoom to 1 so you can immediately see the popup in the small fiddle window
var zoom = 1;
var position = new OpenLayers.LonLat(lon, lat).transform(
"EPSG_WGS84", "EPSG_900913"
);
map.setCenter(position, zoom);
// Finally here's your addPopup code
var query = new OpenLayers.LonLat(
-122.2928337167, 37.5549570333
).transform(
new OpenLayers.Projection("EPSG:4326"),
map.getProjectionObject()
);
var popup = new OpenLayers.Popup.FramedCloud(
"Popup",
query,
// I added a size to make it fit in the small fiddle window
new OpenLayers.Size(100,100),
"Text",
null,
true
);
map.addPopup(popup);
}

Edit existing Google Maps element

For a website I'm using Google Maps to add polylines to a map to display a route. Some routes consist of multiple legs (stages) and I'm trying to add the polylines 'on request'. So only if a user chooses to show a leg, it will draw the polyline. Also the user might choose a completely different route and this new set of polylines should be drawn on the map as well.
My problem is that I can't seem to figure out or find how to select an existing map. I start out by creating a map using the following code:
qMap = new google.maps.Map(document.getElementById(mP.target), mapOptions);
mP.target contains a string with the canvas id and mapOptions is just a object with some options, nothing special.
So I do all kind of stuff with qMap, like adding markers, drawing polylines etc. And this shouldn't just be done at map initiation, but also when the user wants to add something. qMap isn't a global variable and I rather not have it being a global either.
I've tried qMap = google.maps.Map(document.getElementById(mP.target)) and other similar methods. With no success. I'm hoping you can help me out finding a way to this without global variables! Thanks!

There are a couple of things you could try.
1) Wrap your code in an immediately invoked function. This way any variables are contained within the function's scope and don't escape to pollute the global variable space which I guess is your main concern.
(function () {
var mapGlobal = new google.maps.Map(target, options);
function thatDoesSomething(){
// do something with mapGlobal
}
}());
2) Use a static object which might be handy for organising your code.
var Map = {
map: new google.maps.Map(target, options),
thatDoesSomething: function () {
// do something with this.map
}
};
3) Or combine them.
(function () {
var Map = {
map: new google.maps.Map(target, options),
thatDoesSomething: function () {
// do something with this.map
}
};
}());

Creating a map using only toggleable overlays?

I'm trying to create map (using the Google Maps JavaScript API V3) which consists of several partially-transparent layers. By default, these layers should all be overlaid on top of one another to form a complete map, but the user should be able to turn any combination of them on or off (while preserving order) to create whatever view they prefer.
So far, I've had a great deal of luck getting this working for a single layer using map.mapTypes, but when adding all the layers via map.overlayMapTypes, I've hit a couple of snags:
The map doesn't seem to get fully initialized if map.setMapTypeId() is not called (no controls appear and the map is not correctly centered) and it cannot be called with an overlay.
It isn't clear how to toggle the visibility of an overlay without directly modifying the map.overlayMapTypes array, which complicates keeping them correctly ordered. I'd much prefer something analogous to the Traffic/Transit/Photos/etc. control available within Google Maps itself.
Here's the initialize function I'm working with. I'd post a link, but the map imagery isn't publicly available:
function initialize() {
map = new google.maps.Map(document.getElementById("map_canvas"), {
zoom: 0,
center: center
});
/* if these lines are uncommented, the single layer displays perfectly */
//map.mapTypes.set("Layer 3", layers[3]);
//map.setMapTypeId("Layer 3");
//return;
var dummy = new google.maps.ImageMapType({
name: "Dummy",
minZoom: 0,
maxZoom: 6,
tileSize: new google.maps.Size(256, 256),
getTileUrl: function() {return null; }
});
map.mapTypes.set("Dummy", dummy);
map.setMapTypeId("Dummy");
// layers is an array of ImageMapTypes
for (var i = 0; i < layers.length; i++) {
map.overlayMapTypes.push(layers[i]);
}
}
As you can see, I've tried creating a "dummy" maptype (which always returns null for tile URLs) to serve as the base map. While this does cause the controls to display, it still doesn't center correctly.
What's the best way to create a map which consists only of toggleable overlays?
Update: Turns out the dummy maptype works perfectly well if you also remember to set a projection. That's one problem solved, at least. :-)

I use ImageMapType, but I don't add it to mapTypes. I just add it to overlayMapTypes and when I need to remove it I use setAt to set the entry in overlayMapTypes to null.
You will need to add individual controls to the UI that toggle the individual layers.

How can I overlay SVG diagrams on Google Maps?

I would like to add an overlay image on a Google Map. The image is a SVG file I have generated (Python with SVGFig).
I am using the following code:
if (GBrowserIsCompatible()) {
var map = new GMap2(document.getElementById("map_canvas"));
map.setCenter(new GLatLng(48.8, 2.4), 12);
    // ground overlay
    var boundaries = new GLatLngBounds(new GLatLng(48.283188032632829, 1.9675270369830129), new GLatLng(49.187215000000002, 2.7771877478303999));
    var oldmap = new GGroundOverlay("test.svg", boundaries);
map.addControl(new GSmallMapControl());
map.addControl(new GMapTypeControl());
map.addOverlay(oldmap);
}
Surprisingly, it works with Safari 4, but it doesn't work with Firefox (with Safari 3, the background is not transparent).
Does anyone have an idea on how I could overlay an SVG?
PS1: I read some works like this or the source code of swa.ethz.ch/googlemaps, but it seems that they have to use JavaScript code to parse the SVG and add one by one all the elements (but I did not understand all the source...).
PS2: The SVG is composed of different filled paths and circles, with transparency.
If there is no solution to overlay my SVG, I can use 2 alternative solutions:
rasterize the SVG
convert the paths and circles in GPolygons
But I do not really like the 1st solution because of the poor quality of the bitmap and the time to generate it with antialiasing.
And for the 2nd solution, the arcs, ellipses and circles will have to be decomposed into small polylines. A lot of them will be necessary for a good result. But I have around 3000 arcs and circles to draw, so...

Here are some news (I hope it's better to put them here in an answer, instead of editing my questions or to create a new question. Please feel free to move it if needed, or to tell me, so as I can rectify):
My problem was the following:
var oldmap = new GGroundOverlay("test.svg", boundaries);
map.addOverlay(oldmap);
did not work on Safari 3, Firefox and Opera (IE is not enable to draw SVG).
In fact, this code produce the insertion (in a <div>) of the following element
<img src="test.svg" style=".....">
And Safari 4 is able to draw a SVG file as an image, but this is not the way to do for the other browser. So the idea is now to create a custom overlay for the SVG, as explained here.
That's the reason why I asked for this question (I am sorry, but HTML/javascript are not my strongest points).
And since there is a small bug with Webkit for rendering a SVG with transparent background with <object>element, I need to use <object> or <img> accordingly to the browser (I don't like this, but... for the moment, it's still the quick-and-dirty experiments)
So I started with this code (still work in progress):
// create the object
function myOverlay(SVGurl, bounds)
{
this.url_ = SVGurl;
this.bounds_ = bounds;
}
// prototype
myOverlay.prototype = new GOverlay();
// initialize
myOverlay.prototype.initialize = function(map)
{
// create the div
var div = document.createElement("div");
div.style.position = "absolute";
div.setAttribute('id',"SVGdiv");
div.setAttribute('width',"900px");
div.setAttribute('height',"900px");
// add it with the same z-index as the map
this.map_ = map;
this.div_ = div;
//create new svg root element and set attributes
var svgRoot;
if (BrowserDetect.browser=='Safari')
{
// Bug in webkit: with <objec> element, Safari put a white background... :-(
svgRoot = document.createElement("img");
svgRoot.setAttribute("id", "SVGelement");
svgRoot.setAttribute("type", "image/svg+xml");
svgRoot.setAttribute("style","width:900px;height:900px");
svgRoot.setAttribute("src", "test.svg");
}
else //if (BrowserDetect.browser=='Firefox')
{
svgRoot = document.createElement("object");
svgRoot.setAttribute("id", "SVGelement");
svgRoot.setAttribute("type", "image/svg+xml");
svgRoot.setAttribute("style","width:900px;height:900px;");
svgRoot.setAttribute("data", "test.svg");
}
div.appendChild(svgRoot);
map.getPane(G_MAP_MAP_PANE).appendChild(div);
//this.redraw(true);
}
...
The draw function is not yet written.
I still have a problem (I progress slowly, thanks to what I read/learn everywhere, and also thanks to people who answer my questions).
Now, the problem is the following : with the <object> tag, the map is not draggable. All over the <object> element, the mouse pointer is not "the hand icon" to drag the map, but just the normal pointer.
And I did not find how to correct this. Should I add a new mouse event (I just saw mouse event when a click or a double-click append, but not for dragging the map...) ?
Or is there another way to add this layer so as to preserve the drag-ability ?
Thank you for your comments and answers.
PS: I also try to add one by one the elements of my SVG, but... in fact... I don't know how to add them in the DOM tree. In this example, the SVG is read and parsed with GXml.parse(), and all the elements with a given tag name are obtained (xml.documentElement.getElementsByTagName) and added to the SVG node (svgNode.appendChild(node)). But in my case, I need to add directly the SVG/XML tree (add all its elements), and there are different tags (<defs>, <g>, <circle>, <path>, etc.). It is may be simpler, but I don't know how to do.. :(

I spend the last evening on this problem, and I finally found the solution to my problem.
It was not so difficult.
The idea is, as Chris B. said, to load the SVG file with GDownloadUrl, parse it with GXml.parse() and add in the DOM tree every SVG elements I need
To simplify, I have supposed that all the SVG elements was put in a big group called "mainGroup". I have also supposed that some elements can be in the file.
So here is the library, based on the Google Maps Custom Overlays:
// create the object
function overlaySVG( svgUrl, bounds)
{
this.svgUrl_ = svgUrl;
this.bounds_ = bounds;
}
// prototype
overlaySVG.prototype = new GOverlay();
// initialize
overlaySVG.prototype.initialize = function( map)
{
//create new div node
var svgDiv = document.createElement("div");
svgDiv.setAttribute( "id", "svgDivison");
//svgDiv.setAttribute( "style", "position:absolute");
svgDiv.style.position = "absolute";
svgDiv.style.top = 0;
svgDiv.style.left = 0;
svgDiv.style.height = 0;
svgDiv.style.width = 0;
map.getPane(G_MAP_MAP_PANE).appendChild(svgDiv);
// create new svg element and set attributes
var svgRoot = document.createElementNS( "http://www.w3.org/2000/svg", "svg");
svgRoot.setAttribute( "id", "svgRoot");
svgRoot.setAttribute( "width", "100%");
svgRoot.setAttribute( "height","100%");
svgDiv.appendChild( svgRoot);
// load the SVG file
GDownloadUrl( this.svgUrl_, function( data, responseCode)
{
var xml = GXml.parse(data);
// specify the svg attributes
svgRoot.setAttribute("viewBox", xml.documentElement.getAttribute("viewBox"));
// append the defs
var def = xml.documentElement.getElementsByTagName("defs");
//for( var int=0; i<def.length; i++)
svgRoot.appendChild(def[0].cloneNode(true));
//append the main group
var nodes = xml.documentElement.getElementsByTagName("g");
for (var i = 0; i < nodes.length; i++)
if (nodes[i].id=="mainGroup")
svgRoot.appendChild(nodes[i].cloneNode(true));
});
// keep interesting datas
this.svgDiv_ = svgDiv;
this.map_ = map;
// set position and zoom
this.redraw(true);
}
// remove from the map pane
overlaySVG.prototype.remove = function()
{
this.div_.parentNode.removeChild( this.div_);
}
// Copy our data to a new overlaySVG...
overlaySVG.prototype.copy = function()
{
return new overlaySVG( this.url_, this.bounds_, this.center_);
}
// Redraw based on the current projection and zoom level...
overlaySVG.prototype.redraw = function( force)
{
// We only need to redraw if the coordinate system has changed
if (!force) return;
// get the position in pixels of the bound
posNE = map.fromLatLngToDivPixel(this.bounds_.getNorthEast());
posSW = map.fromLatLngToDivPixel(this.bounds_.getSouthWest());
// compute the absolute position (in pixels) of the div ...
this.svgDiv_.style.left = Math.min(posNE.x,posSW.x) + "px";
this.svgDiv_.style.top = Math.min(posSW.y,posNE.y) + "px";
// ... and its size
this.svgDiv_.style.width = Math.abs(posSW.x - posNE.x) + "px";
this.svgDiv_.style.height = Math.abs(posSW.y - posNE.y) + "px";
}
And, you can use it with the following code:
if (GBrowserIsCompatible())
{
//load map
map = new GMap2(document.getElementById("map"), G_NORMAL_MAP);
// create overlay
var boundaries = new GLatLngBounds( new GLatLng(48.2831, 1.9675), new GLatLng(49.1872, 2.7774));
map.addOverlay( new overlaySVG( "test.svg", boundaries ));
//add control and set map center
map.addControl(new GLargeMapControl());
map.setCenter(new GLatLng(48.8, 2.4), 12);
}
So, you can use it exactly as you use the GGroundOverlay function, except that your SVG file should be created with the Mercator projection (but if you apply it on small area, like one city or smaller, you will not see the difference).
This should work with Safari, Firefox and Opera. You can try my small example here
Tell me what do you think about it.

This question was briefly discussed on the Google Maps API Group. Here's what they said:
I've not tried it, but SVG is a subset
of XML, so you can read them with
GDownloadUrl() and analyse them with
GXml.parse(). On some wonky webservers
you may have to change the file
extension to XML.
You then have to crawl through the XML
DOM, writing the SVG that you find
with document.createElementNS() and
.setAttribute() calls...
There are also a some Google Maps SVG examples here and here.
Good luck!