Develop Reference

Get JSON WebMap from ArcGIS JavaScript API Map object

I'm trying to get a WebMap object (as JSON) from a JavaScript Map object in the ArcGIS JavaScript API. Is there any way to do this within the API, without using ArcGIS.com? Ideally something like:
webMapAsJSON = map.toWebMap();
From the "Export Web Map Task" documentation in the REST API, there's this line that suggests it should exist:
"The ArcGIS web APIs (for JavaScript, Flex, Silverlight, etc.) allow developers to easily get this JSON string from the map."
However, I don't see anything in the Map object or elsewhere in the API that would do this.

You can't. At least not officially. The steps outlined below are not recommended. They use part of the ArcGIS JS library that is not part of the public API and therefore this behavior may not work in the next version of the API or they may back-patch a previous version of the API and this could stop working even on something that previously did work.
That said, sometimes you need some "future" functionality right now and this is actually a pretty straightforward way of getting what you want using the common proxy pattern
Use the undocumented "private" function _getPrintDefinition
var proxy_getPrintDefinition = printTask._getPrintDefinition;
printTask._getPrintDefinition = function() {
var getPrintDefResult = proxy_getPrintDefinition.apply(this, arguments);
//Now you can do what you want with getPrintDefResults
//which should contain the Web_Map_as_JSON
console.log(Json.stringify(getPrintDefResult));
//make sure you return the result or you'll break this print task.
return getPrintDefResult;
}
_getPrintDefinition takes the map as the first argument and a PrintParameters object as the second.
so you'll have to create a PrintTask, redefine the _getPrintDefinition function on the newly created print task as outlined above, create a PrintParameters and then run:
myPrintTask._getPrintDefinition(myMap,myPrintParameters);
The results of this on my little test are:
{"mapOptions":{"showAttribution":false,"extent":{"xmin":-7967955.990468411,"ymin":5162705.099750506,"xmax":-7931266.216891576,"ymax":5184470.54355468,
"spatialReference":{"wkid":102100,"latestWkid":3857}},"spatialReference":{"wkid":102100,"latestWkid":3857}},
"operationalLayers":[
{"id":"layer0","title":"layer0","opacity":1,"minScale":591657527.591555,"maxScale":70.5310735,"url":"http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"},
{"id":"XXX-Redacted-XXX","title":"serviceTitle","opacity":1,"minScale":0,"maxScale":0,"token":"XXX-Redacted-XXX","url":"http://XXX-Redacted-XXX/arcgis/rest/services/TestService/MapServer"},
{"id":"XXX-Redacted-XXX","opacity":1,"minScale":0,"maxScale":0,"featureCollection":{"layers":[]}},
{"id":"featureGraphics","opacity":1,"minScale":0,"maxScale":0,"featureCollection":{"layers":[]}},
{"id":"map_graphics","opacity":1,"minScale":0,"maxScale":0,"featureCollection":{"layers":[]}}
]}
if you don't need to do any operations on the web map json and just need the output then you don't even need to use the proxy pattern.

#Suttikeat Witchayakul's answer above should work if your goal is to print the map using a print service.
However, if you are trying to export the map to the web map JSON spec so that you can save it to ArcGIS Online/Portal, or re-instantiate a map object from it later, you may have some problems. This is because the web map specification is not the same as the export web map specification, which what the print task generates and sends to printing services.
Unfortunately, the ArcGIS API for JavaScript does not provide any methods to export a map object to web map JSON. This is supposed to be coming in version 4... at some point. Until then, you can use the all but abandoned cereal library. However, if your map uses layer types that are not fully supported by cereal, it may not work for you as is and you would have to extend it.

If you want to use "esri/tasks/PrintTask" to export your map, you must use "esri/tasks/PrintParameters" for execute the printTask. Just set your map object directly to printParameter.
require([
"esri/map", "esri/tasks/PrintTemplate", "esri/tasks/PrintParameters", ...
], function(Map, PrintTemplate, PrintParameters, ... ) {
var map = new Map( ... );
var template = new PrintTemplate();
template.exportOptions = {
width: 500,
height: 400,
dpi: 96
};
template.format = "PDF";
template.layout = "MAP_ONLY";
template.preserveScale = false;
var params = new PrintParameters();
params.map = map;
params.template = template;
printTask.execute(params, printResult);
});

Fire Event to Open CartoDB/Leaflet Marker

I've got a pretty specific question that I'm not really expecting a direct answer to, but any guidance will be helpful.
Simple and plain, I want to programmatically fire a click event on a marker positioned on a Leaflet map, powered by CartoDB. I have a single layer on the map that contains markers, and each marker has click events associated with them. So, essentially, I just need to find the marker and fire the click event on it.
For context, Mapbox actually does exactly this, but unfortunately I can not use Mapbox for this particular implementation:
https://www.mapbox.com/mapbox.js/example/v1.0.0/open-popup-externally/
I'm open to suggestions, but preferably, I'd like to do something similar to the code in the link above -- interrogate either Leaflet or CartoDB via javascript to find and access the marker via custom properties/lat-lng/??. I figure it would be simple enough to go from there.
Another way could be to hook an event when the markers are created, store them in a hash, then access that storage when I need to do my manual click. However, I don't know of any such event that exists, and I can't locate documentation that lists supported events.
Since I'm not creating the markers myself, and can not (for reasons), storing them as I add them to the map is not an option here.
I assume since Mapbox is doing it, there must be some hook, but I can't find any valuable documentation to point me in the right direction.
Any suggestions or pointers?

To anyone who stumbles upon this, I've got a workable solution for my particular case. This call will do it for you:
layer.trigger 'featureClick', event, latlng, pos, data, layer_count
Essentially, you'll want to grab the layer in question and trigger the click, passing the appropriate data:
event: this can be null, since there is no event
latlng: the lat/long position
data: an object like { cartodb_id: 123 }. The cartodb_id is required.
layer_count: the index of your layer (probably 0)
To grab the latlng and the cartodb_id here, you'll probably need to do what I did -- query for it:
function openMarker(layer, my_object_id) {
vars = { database_id: my_object_id };
opts = { format: 'geojson' };
query = "SELECT * FROM my_table WHERE my_object_id = {{ my_object_id }}"
sql = new cartodb.SQL({user: my_user_id});
sql.execute(query, vars, opts).done(function(data) {
if (data.features != undefined && data.features.length == 1)
row = data.features[0];
latlng = [ row.geometry.coordinates[1], row.geometry.coordinates[0] ];
layer.trigger('featureClick', null, latlng, null, { cartodb_id: row.properties.cartodb_id }, 0);
});
}
Then, you can just call open_marker, passing the layer you wish to open the marker on and your object identifier. As long as that's in your cartodb database, you can grab it. Of course, the query can be adjusted to suit your means.
For my particular implementation, I had to use a setTimeout call to get the flow of control right, as I do my calls on page load. But if you're calling after the page has loaded, should be no problem.
So, simple enough way to open a marker given a local identifier. Hope this helps someone else!
Kudos for the inspiration for this solution go to:
https://gist.github.com/javisantana/7b817fda1e7511c451c7#file-index-html-L39

Styling a geoJSON Feature Layer in MapBox

I just started playing with MapBox and am running into a confusing issue. I'm creating a map with a geoJSON layer using this code:
var map = L.mapbox.map('map', '<MapBoxID>');
var zipLayer = L.mapbox.featureLayer('data/blah.json');
zipLayer.addTo(map);
zipLayer.setStyle({color: 'red'});
The map appears and shows the geoJSON, but it ignores the styling. When I copy that last line into the JS console in my browser, it works fine, though.
What am I missing here? Also, I've tried at least a dozen different ways of including the style in the options directly in the featureLayer() call, but nothing has worked. How do I specify the style when creating the feature layer?

I'm guessing a bit here, since I don't know the Mapbox JS very well, but it sounds a lot like an async error. Strangely, I don't see anything in the Mapbox or Leaflet APIs about a callback for this function. But, you can pass straight GeoJSON to featureLayer(), so I'd suggest using jQuery (or your XHR library of choice) to grab the data:
var map = L.mapbox.map('map', '<MapBoxID>');
var zipLayer;
$.getJSON('data/blah.json', function(data) {
zipLayer = L.mapbox.featureLayer(data);
zipLayer.addTo(map);
zipLayer.setStyle({color: 'red'});
});
Hopefully that'll do the trick.

I would go the route of using the built-in featureLayer function, then listening for it to be ready. This should help get you pointed in the right direction:
var featureLayer = L.mapbox.featureLayer()
.loadURL('/example-single.geojson')
.on('ready', function(layer) {
this.eachLayer(function(marker) {
// See the following for styling hints:
// https://help.github.com/articles/mapping-geojson-files-on-github#styling-features
marker.setIcon(L.mapbox.marker.icon({
'marker-color': '#CC0000'
}));
});
})
.addTo(map);

Have you tried adding the zipLayer after setting the style?

AngularJS Google Map directive map instance

I'm using http://angular-google-maps.org/ it's nice angular google maps library. But i want use map instance which is loaded not in angularjs context by something like this:
$scope.map = {
events: {
tilesloaded: function (map) {
$scope.$apply(function () {
$scope.mapInstance = map;
});
}
}
}
Ok nice i have mapInstance and I CAN use it programmatically. But in application lifecycle this fire to late- so in other words I want to load whole directive (and get map instance) before other code- where I just wan't to use other map events.

In recently looking up ways to get the map instance from the example on the docs page, I came across this instead:
$scope.map.control.getGMap().
Make sure on your google-maps HTML markup, you have the options attribute set as control="map.control" and an empty object set in your $scope.map object.
$scope.map= { control : {}, ...other map options...};
That empty objects is filled when google map is initiated. I hope this helps and isn't too late.
Enjoy Angular!!!

leaflet js: draw POIs as canvas

I want to draw many geo points with Leaflet. Therefore I want to use HTML5 canvas to improve the performance.
My datasoure is geoJSON. As I saw in the documention of Leaflet, it is not possible to draw the geo positions as canvas yet.
var anotherGeojsonLayer = new L.GeoJSON(coorsField, {
pointToLayer: function (latlng){
return new L.Marker(latlng, {
icon: new BaseballIcon()
});
}
});
I think I should hook up here:
pointToLayer: function (latlng) { }
Does somebody know how to draw my latlng objects as canvas?

I'm Leaflet author. You can do this by using L.CircleMarker instead of regular Marker, and also using an experimental L_PREFER_CANVAS switch to render vectors as Canvas (instead of SVG), like this: https://github.com/CloudMade/Leaflet/blob/master/debug/vector/vector-canvas.html

Expanding on the original answer in case anyone needs this for Leaflet 1.0. You should still use L.circleMarker() (Leaflet circleMarker documentation) instead of L.marker(), but the way to use the canvas has changed.
In Leaflet 1.0, the experimental L_PREFER_CANVAS switch has been upgraded to an official map option preferCanvas (Leaflet preferCanvas documentation).
var map = L.map('mapid', {
preferCanvas: true
});
Alternatively, you can explicitly set the canvas renderer; I think this does the same thing as the preferCavas option. Here's the Leaflet documentation for canvas.
var map = L.map('mapid', {
renderer: L.canvas()
});
Either of these options (preferCanvas: true or renderer: L.canvas()) with L.circleMarker() was significantly faster than a regular layer using L.marker().