Load or display differents geojson data on zoom level for leaflet maps

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.6.4/leaflet.css">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
<script src="http://cdn.leafletjs.com/leaflet-0.6.4/leaflet.js"></script>
<script src="http://leafletjs.com/examples/sample-geojson.js"></script>
<body onload="init()">
    Leaflet load Layers with dropdown choice
    <div id="info"></div>
    
    <select name="Layerchoice" id="select1" onchange="dropdown_onchange(this.value)">
        <option value="dummy" disabled  selected>Please select</option>
        <option value="testlayer1">Testlayer1</option>
        <option value="testlayer2">Testlayer2</option>
    </select>
    
    <div id="map"></div>Data from http://leafletjs.com/examples/geojson.html</body>

CSS

html {
          height: 100%
      }
      body {
          height: 100%;
          margin: 0;
          padding: 0;
      }
      #info {
          margin:10px;
      }
      #map {
          height: 85%;
          margin-top:10px;
          border: 1px solid grey;
      }
      #zoomlevel {
          color:green;
          font-weight:bold;
      }
      #layername {
          color:orange;
          font-weight:bold;
      }

JavaScript

var map, layerControl;

var dropdownlayers = {};
dropdownlayers[choice=="testlayer1"] = 
    {
    name: "Testlayer1",
    layer: L.geoJson(),
    url: "https://gist.githubusercontent.com/anonymous/6622d04d71ed2dd7927a/raw/0eb6c1145cbd60a050d8e46c2a7805504b901d7d/us_states.js"
}
;

dropdownlayers[choice=="testlayer2"] = 
    {
    name: "Testlayer2",
    layer: L.geoJson(),
    url: "https://gist.githubusercontent.com/anonymous/559d9a178f4b8ed90518/raw/a65e110c173737af958a481b33feeef57bba5b4a/geojsontest.js"
}
;

function init() {
    map = L.map('map').setView([39.74739, -105], 11);

    var osmUrl = 'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png';
    var osmAttrib = 'Map data © <a href="http://openstreetmap.org">OpenStreetMap</a> contributors';
    var osm = new L.TileLayer(osmUrl, {
        attribution: osmAttrib
    }).addTo(map);


    var coorsLayer = L.geoJson(coorsField, {

        pointToLayer: function (feature, latlng) {
            return L.marker(latlng, {

            });
        }
    }).addTo(map);

	var baseLayers = {
    "OpenStreetMap": osm
};

var overlays = {
    
};

layerControl= L.control.layers(baseLayers, overlays,{collapsed:false}).addTo(map);

} // end init

function clean_map() {
    map.eachLayer(function (layer) {
        if (layer instanceof L.GeoJSON)
        //Do marker specific actions here

        {
            layerControl.removeLayer(layer);
			map.removeLayer(layer);

        }
        console.log(layer);


    });
}



function load_layer(dropdownchoice) {
	clean_map();
    $.ajax({
        dataType: "json",
        url: dropdownchoice.url,
        success: function (data) {
            var layer = dropdownchoice.layer;
            layer.clearLayers();
            layer.addTo(map);
            $(data.features).each(function (key, data) {
                layer.addData(data);
            });
           
            layerControl.addOverlay(layer, dropdownchoice.name);
            map.fitBounds(layer.getBounds());
       ...