Update json node

/**
 * Update a json node of an object
 * Could create needed nodes, if path not exists
 * @param {object} obj - the object that should be updated
 * @param {string} path - the path of the node that should be updated
 * @param value - the new value for the node
 * @param {bool} createNodes - if true, the missing nodes will be created - if false, a error will be thrown if any of the nodes in the path is missing
 */
var updateJson = function (obj, path, value, createNodes) {
    if (obj === undefined) { obj = {}; }
    if (path === undefined) { path = ''; }
    if (createNodes === undefined) { createNodes = false; }

    if (path.indexOf('.') > -1) {
        // not a the node you are looking for.

        if (obj[path.substr(0, path.indexOf('.'))] === undefined) {
            // the node you are looking for does not exists.
            if (createNodes === false) { return new Error("path not valid - missing node " + path); }
            obj[path.substr(0, path.indexOf('.'))] = {};
        }

        var nPath = path.substr(path.indexOf('.') + 1);
        var nObj = obj[path.substr(0, path.indexOf('.'))];
        obj[path.substr(0, path.indexOf('.'))] = updateJson(nObj, nPath, value, createNodes);
        return obj;
    } else {
        obj[path] = value;
        return obj;
    }
};