Question

I don’t think this is possible from what I read, but is there away to check if my map marker is null in the following code? I read something about prototypes, but I’m not sure if that’s what I need to use. Here is the code:

this.currentLocation = function(latitude, longitude) {
    if (loc_marker != null) {
        loc_marker.setPosition(new google.maps.LatLng(latitude, longitude);
    }
    else {
        var loc_marker = new google.maps.Marker({
            position: new google.maps.LatLng(latitude, longitude),
            title: "Here"
        });
        loc_marker.setMap(map); 
    }           
};

I’m trying to move a marker on a Google Map each time the location changes. I want to check to see if a marker has been set, and if it has then I’ll just change the position using setPosition();

If you have any suggestions I’d really appreciate it!

Answer 1

All of the following will do what you’re looking for…

if (loc_marker != null) {  //Tests for null and for undefined
if (loc_marker === null) { //Tests for null
if (typeof loc_marker === 'object' && loc_marker === null) {  //Another null test, albeit redundant
if (typeof loc_marker === 'undefined') {  //Tests for undefined
if (loc_marker) { //Test for a defined non-null value

That said, where is loc_marker actually defined? It looks “like” you’re trying to define it in the else block (although JavaScript doesn’t work that way).

Save for where you’re declaring loc_marker, the code you have should work fine.

Hope this helps,

Pete