I am making a web mapping app using leaflet and some geoJSON data for a grid. I want to be able to mouseover each grid cell and both highlight that cell AND show a popup of the coordinates. In the code below, I have basically created two functions that should be triggered when the mouseover event occurs: highlightFeature(e) and coordinate(e). After my getJSON request to grab the geoJSON data for the grid, I am using layer.on({mouseover: <function call>}) to call the desired function when I mouseover a feature/grid cell. If I just use one function, it works fine. But if I try to do something likemouseover: highlightFeature, coordinate,` only the first function works. What am I doing wrong?

function highlightFeature(e) {
      var layer = e.target;

        weight: 0.5,
        fillColor: "#ffff00",
        dashArray: '',
        fillOpacity: 0.5

      if (!L.Browser.ie && !L.Browser.opera) {

function resetHighlight(e) {
  var layer = e.target;

    weight: 0.5,
    dashArray: '',
    fillOpacity: 0

function zoomToFeature(e) { 

var popup = L.popup();
function coordinate(e) {
  var layer = e.target;

    .setContent("Coordinates: " + feature.properties.LON + ", " +   feature.properties.LAT.toString())

$.getJSON('./grid.geojson', function(data){
// add GeoJSON layer to the map once the file is loaded
  L.geoJson(data, {
    style: function(feature){
      return {
        color: "#000000",
        weight: 0,
        opacity: 0,
        fillOpacity: 0
    onEachFeature: function( feature, layer ){
        mouseover: highlightFeature, coordinate,
        mouseout: resetHighlight,
        click: zoomToFeature

1 Answer 1


JavaScript is error-tolerant only to some extent.

It does not like your 2 function names separated by a comma.

You know that in JS, whitespace / line breaks do not have a particular meaning besides separating identifiers and statements. You also know that in JS, an object is made of a list of property names and values.

Therefore, the mouseover property expects a single value, but you are trying to provide 2, which results in a syntax error in ES5, or equivalent to {coordinate: coordinate} in ES6 (shorthand assignment).

You could either make up a "wrapper" function that would call your 2 functions:

layer.on("mouseover", function (event) {

Or you could also simply call another layer.on() to attach your 2nd function to the same event:

layer.on("mouseover", highlightFeature);
layer.on("mouseover", coordinate);
  • 1
    This worked perfectly. I went with option #2; I just did 2 layer.on("mouseover", ...) calls. Both the highlight and the tooltip displays now.
    – gwydion93
    Commented Aug 8, 2016 at 14:46

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