gistfile1.js

function doActionOnLayer(layerName, functionName) {
    for (var i = 0; i < numberOfLayers; i++) { 
        var customName = layerName; //layerName should be string
        var myLayer = app.activeDocument.layers[i];
        var myLayer = myLayer.name;
        if (customName == myLayer) {
            var myLayerIndex = i;
            return myLayerIndex;
            functionName;
        }
        else { break; } 
    }
}

function testFunction() {
    var alertL = app.activeDocument.layers[myLayerIndex];
    var alertL = alertL.name; 
    alert(alertL); //this is to test concept
}

//run the action
doActionOnLayer("note", testFunction());