Force zIndex of Leaflet Marker

leaflet.forceZIndex.js

// Force zIndex of Leaflet
(function(global){
  var MarkerMixin = {
    _updateZIndex: function (offset) {
      this._icon.style.zIndex = this.options.forceZIndex ? (this.options.forceZIndex + (this.options.zIndexOffset || 0)) : (this._zIndex + offset);
    },
    setForceZIndex: function(forceZIndex) {
      this.options.forceZIndex = forceZIndex ? forceZIndex : null;
    }
  };
  if (global) global.include(MarkerMixin);
})(L.Marker);

Thanks for this! I was going crazy trying to figure out what I was missing with zIndexOffset. I eventually figured out that it works properly for default Leaflet icons... but as soon as you apply a custom "iconUrl", zIndexOffset becomes unpredictable or doesn't work at all.

Your "setForceZIndex" function does exactly what the standard Leaflet code claims to do, but doesn't.

Thank you very much!!!

I observed the same unpredictable z-index calculation @gpsvisualizer mentioned, bar the proper functionality of the default icons.
After dragging my location-marker a few times arround, the z-index changed from some_large_value to -other_large_value.

Not anymore.

Let me add little fix, to allow forceZIndex = 0. Check whether forceZIndex is assigned with isNaN(). Any numeric should be considered as good value.

    _updateZIndex: function(offset) { // offset at relative value, or put absolute zIndex value with forceZIndex
        this._icon.style.zIndex = isNaN(this.options.forceZIndex) // any no-numeric = unassigned. 0 is ok for the forceZIndex
            ? (this._zIndex + offset)
            : (this.options.forceZIndex + (this.options.zIndexOffset || 0))
    },