Leaflet: Including metadata with CircleMarkers - javascript

I have a Leaflet map that I am populating with CircleMarkers. I would like to include an additional value (a database ID) with each circle so that when I click on the circle, I can get the value and navigate somewhere else.
I would like to add the value directly to the marker and use a callback function on the entire featureGroup instead of adding a callback function to each marker, since we're dealing with over 500 markers and it would be a performance drag.
Worth mentioning: I'm using Typescript inside an Angular app, but it's still Leaflet.
What I've tried:
var data = [
{lat: 20.45, lng: -150.2, id: 44},
{lat: 23.45, lng: -151.7, id: 45},
]
var points = [];
data.forEach((d) => {
// How do I add an additional variable to this circleMarker?
points.push(circleMarker(latLng(d.lat, d.lng), { radius: 5}));
})
var group = featureGroup(points);
group.on("click", function (e) {
console.log(e);
// This is where I would like to get the ID number of the record
});

FWIW, you have plenty ways of adding your own data to Leaflet Layers (nothing specific to Circle Markers, it is the same for Markers, but also Polygons, Polylines, etc.).
See for instance: Leaflet/Leaflet #5629 (Attach business data to layers)
In short, there are mainly 3 possible ways:
Just directly add some properties to the Leaflet Layer after it has been instantiated. Make sure you avoid collision with library properties and methods. You can add your own prefix to the property name to decrease the chance of collision.
var marker = L.marker(latlng);
marker.myLibTitle = 'my title';
Use the Layer options (usually the 2nd argument of the instantiation factory), as shown by #nikoshr. As previously, avoid collision with library option names.
L.marker(latlng, {
myLibTitle: 'my title'
});
Use the Layer GeoJSON properties. Leaflet does not use those for internal purpose, so you have total freedom of this data, without any risk of collision.
L.Layer.include({
getProps: function () {
var feature = this.feature = this.feature || {}; // Initialize the feature, if missing.
feature.type = 'Feature';
feature.properties = feature.properties || {}; // Initialize the properties, if missing.
return feature.properties;
}
});
var marker = L.marker(latlng);
// set data
marker.getProps().myData = 'myValue';
// get data
myFeatureGroup.on('click', function (event) {
var source = event.sourceTarget;
console.log(source.getProps().myData);
});

Events fired on members of a FeatureGroup are propagated to the FeatureGroup object
Event objects expose a sourceTarget member giving you access to the source marker
Options in a layer can be accessed as marker.options
From there, you could pass your id as a member of the options object when building your markers and retrieve this value when a marker is clicked. For example:
var points = data.map((datum) => {
return L.circleMarker(datum, {radius: 5, id: datum.id});
});
var group = L.featureGroup(points);
group.addTo(map);
group.on("click", (e) => {
console.log(e.sourceTarget.options.id);
});
And a demo
var data = [
{lat: 20.45, lng: -150.2, id: 44},
{lat: 23.45, lng: -151.7, id: 45},
]
var points = [];
var map = L.map('map', {
center: [20.45, -150.2],
zoom: 4
});
var points = data.map(function (datum) {
return L.circleMarker(datum, {radius: 5, id: datum.id});
});
var group = L.featureGroup(points);
group.addTo(map);
group.on("click", function (e) {
console.log(e.sourceTarget.options.id);
});
html, body {
height: 100%;
margin: 0;
}
#map {
width: 100%;
height: 150px;
}
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.3.1/leaflet.css"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.3.1/leaflet.js"></script>
<div id='map'></div>

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Thanks to #Kevin B's advice to use recursion, this is how I fixed my code to make it work.
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I'm right now building a custom Knockout.js binding to handle drawing of polygons. In this case the Knockout API only gives me a reference to a DOM object to access whatever it is I need to update. However, it looks like by design leaflet.js wants the user to store the map instance in their implementation. I don't have that option.
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By request here's the custom binding, please note it's a work in progress:
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element.myMapProperty = map;
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attribution: '© OpenStreetMap contributors'
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To use the binding handler you would just bind like the following:
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I have only tested this jsfiddle in Internet Explorer 11, Firefox 26.0 and Firefox 27.0.1.
noting that in very limited circumstances, this could be a solution: https://stackoverflow.com/a/60836683/1116657
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accessing marker from listener-Google maps javascript API3.0

I have several markers (in an array) on my map, each with a custom ID tag i've given them.
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When I click on a marker, i wish to add it's ID to another array.
The problem:
The mouse event from Google does not have a target attribute, only the position, so I can't seem to access the ID directly.
I don't really want to have to resort to using the position to find the closest marker to it and returning it's ID this way, it's rather convoluted.
All help is appreciated
This is really easy, thanks to a feature in JavaScript and many other languages called a closure.
Simply put the code that creates the marker and sets up its event listener(s) insidea function, and call that function for each marker with the data needed for that specific marker. For example:
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I didn't test this Maps API code, but the specifics of the code are not important. What is important to understand is that place variable you see used in the code. This is the key part: that variable is accessible inside the event listener, simply because the event listener is nested inside the addPlace() function which has place as a parameter.
Note the difference between that code and code like this, which will not work:
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The only difference between the two is that the working version puts the loop body in a separate function which is called from the loop, instead of having all that code directly inside the loop. Having that code in a function that you call each time is what creates the closure, and that's what lets the inner event listener function "see" the variables in the outer function.
The great thing about closures is that you can use them in any similar situation. It isn't specific to the Maps API or the objects that the API uses. You may have even used them already and not realized it, for example in a setTimeout() call like this:
// Display an alert 'time' milliseconds after this function is called
function slowAlert( message, time ) {
setTimeout( function() {
alert( message );
}, time );
}
slowAlert( 'Howdy!', 1000 ); // Wait a second and then say Howdy!
Where the alert() call is made inside the setTimeout() callback function is made, it's using the closure on the slowAlert() function to pick up the value of the message variable that was passed into that function.
This should help. I added a customId property to the marker object and then in the marker click event I assign the id property to the new array.
function initialize() {
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var centerPosition = new google.maps.LatLng(38.713107, -90.42984);
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zoom: 6,
center: centerPosition,
mapTypeId: google.maps.MapTypeId.ROADMAP
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var bounds = new google.maps.LatLngBounds();
map = new google.maps.Map($('#map')[0], options);
var infoWindow = new google.maps.InfoWindow();
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var markers = [];
//sencondary array to store markers that were clicked on.
var markerIdArray = [];
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var lat = 38.713107 + Math.random();
var lng = -90.42984 + Math.random();
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map: map,
position: new google.maps.LatLng(lat, lng),
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});
bounds.extend(marker.position);
google.maps.event.addListener(marker, 'click', function () {
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}
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Here is an example of this in action.

Problems calling fitbounds outside jquery.each()

I'm working on a Google Map in JavaScript(v3).
I need to show some markers from XML, for which I use jQuery.
Here's the object and function, might save me time explaining:
var VX = {
map:null,
bounds:null
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$.get(filename, function(xml) {
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I declare the bounds when I initialize the map... haven't included the entire code because its like 300 lines.
Shouldn't I be able to use a value that I passed to a global object?
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Place the fitBounds inside the get() handler, but outside the each() function. Like so:
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map:null,
bounds:null
}
VX.placeMarkers = function(filename)
{
$.get
(
filename,
function(xml)
{
$(xml).find("marker").each
(
function()
{
var lat = $(this).find('lat').text();
var lng = $(this).find('lng').text();
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VX.bounds.extend(point);
//VX.map.fitBounds(VX.bounds); //this works
var marker = new google.maps.Marker
({
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}
);
VX.map.fitBounds(VX.bounds); //-- This should work.
}
);
//VX.map.fitBounds(VX.bounds); //this shows me the ocean east of africa
}

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