[GIS] OpenLayers hide layer function

openlayers-2

I need to hide a layer with a function, use this script:

function hideLayer(layerName) {
        layerName.setVisibility(false);
}

I have this error: 'map' is null or undefined

my code page:

var map;
var lon =9.10;
var lat =45.46;
var zoom =10;
function init(){ 
    epsg4326 = new OpenLayers.Projection("EPSG:4326")
    map = new OpenLayers.Map("map", {displayProjection:epsg4326,
    controls: [
        new OpenLayers.Control.Navigation(),
        new OpenLayers.Control.MousePosition(),
        new OpenLayers.Control.LayerSwitcher()
        ]
    });
var newLayer = new OpenLayers.Layer.OSM("Mappa locale", "Tiles/${z}/${x}/${y}.png", {numZoomLevels: 19, alpha: false, isBaseLayer: true});
 map.addLayer(newLayer);
 var layer = new OpenLayers.Layer.Vector("Mezzi disponibili", {
   strategies: [new OpenLayers.Strategy.BBOX({resFactor: 1.1})],                    
   protocol: new OpenLayers.Protocol.HTTP({
       url: "./sinottico_mezziliberi.txt",
       format: new OpenLayers.Format.Text()
        })
    });
map.addLayer(layer);

Best Answer

If you indent your code better you could find the errors easier.

Your correct code would be:

var map;
var lon =9.10;
var lat =45.46;
var zoom =10;

function init(){ 
    epsg4326 = new OpenLayers.Projection("EPSG:4326");
    map = new OpenLayers.Map("map", {
        displayProjection:epsg4326,
        controls: [
            new OpenLayers.Control.Navigation(),
            new OpenLayers.Control.MousePosition(),
            new OpenLayers.Control.LayerSwitcher()
        ]
    });
}
var newLayer = new OpenLayers.Layer.OSM("Mappa locale", "Tiles/${z}/${x}/${y}.png", {numZoomLevels: 19, alpha: false, isBaseLayer: true});
map.addLayer(newLayer);

var layer = new OpenLayers.Layer.Vector("Mezzi disponibili", {
    strategies: [new OpenLayers.Strategy.BBOX({resFactor: 1.1})],                   
    protocol: new OpenLayers.Protocol.HTTP({
        url: "./sinottico_mezziliberi.txt",
        format: new OpenLayers.Format.Text()
    })
});
map.addLayer(layer);
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