[js] Firebase Update Node and keep existing values

firebase_updateNode.js

//use
var record = {};
record['testfield1'] = "test1";
record['testfield2'] = "test2";
record['testfield3'] = "test3";

var preserveNodes = ['ccategories', 'stats', 'competitions', 'causes', 'companies'];

updateNode('https://' + baseURL + '/testcat/' + $('#oTESTCAT_updateID').val(), record, preserveNodes, null)


//
function updateNode(url, itemOBJ, preserveColsArray, priority) {
	console.log('url' + url);

	var upd2DB = new Firebase(url);

	$.when(upd2DB.transaction(function(current_value) {

		if (current_value != null) { //defeat - The update function in a transaction can be called multiple times
			if (preserveColsArray) {
				for (var i = 0; i < preserveColsArray.length; i++) {
					//only when snapshot^ contains the specific node/field
					if (current_value[preserveColsArray[i]])
						itemOBJ[preserveColsArray[i]] = current_value[preserveColsArray[i]];
				}
			}
		}
		return itemOBJ;
	})).done(function(x) {
		//console.log(new Date() + "updated!");
	});

	if (priority) {
		$.when(upd2DB.setPriority(priority)).done(function(x) {
		});
	}
}