Heatmap from geojson points in leaflet - leaflet

Question

I am attempting to create a simple heatmap from a feature collection of points using leaflet's heatmap plugin. After successfully getting the json data from an ajax call, I create an empty coords array and push coordinates from each feature.
However, this method does not work and neither does the geojson2heat function. There are no errors in the console. What am I doing wrong and does anyone know of a workaround?
var map = L.map('map').setView([50.0647, 19.9450], 12);
var tiles = L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
attribution: '© OpenStreetMap contributors',
}).addTo(map);
var geojsonLayer = new L.GeoJSON.AJAX("newmap.geojson");
coords = [];
function onEachFeature(feature, layer) {
coords.push(feature.geometry.coordinates);
};
L.GeoJSON(geojsonLayer, {
onEachFeature: onEachFeature
})
var heat = L.heatLayer(coords).addTo(map);
The structure of the geojson is standard:
{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
"features": [
{ "type": "Feature", "properties": { "st_x": 19.952030181884801, "st_y": 50.055513141929701 }, "geometry": { "type": "Point", "coordinates": [ 19.952030181884801, 50.055513141929701 ] } },
{ "type": "Feature", "properties": { "st_x": 18.672015, "st_y": 50.287181666666697 }, "geometry": { "type": "Point", "coordinates": [ 18.672015, 50.287181666666697 ] } },

Answer 1

I am mostly doing the same as you but with Mapbox, which is based on Leaflet.
The problem I had is that the latitude and longitude coordinates of the GeoJSON were reversed. There were no errors on console either- points were just not showing on map. So, you need:
"coordinates": [ longitude, latitude ]
Hope that's the issue.