JavaScript でネストされたオブジェクトのプロパティを動的に設定するにはどうすればよいですか?

<code class="javascript">function set(path, value) {
    var schema = obj;  // Reference to internal objects within obj
    var pList = path.split('.');
    var len = pList.length;
    for (var i = 0; i < len - 1; i++) {
        var elem = pList[i];
        if (!schema[elem]) schema[elem] = {};
        schema = schema[elem];
    }

    schema[pList[len - 1]] = value;
}</code>

<code class="javascript">set('db.mongodb.user', 'root');</code>

<code class="javascript">var obj = {
    db: {
        mongodb: {
            host: 'localhost'
        }
    }
};</code>

<code class="javascript">obj = {
    db: {
        mongodb: {
            host: 'localhost',
            user: 'root'
        }
    }
};</code>