Unable to set values in javascript array

I am unable to set project activities which are inside clientsData. Here is my scenario

By the time the control reaches inside my callback function of executeSql, values of i and j are maximum possible values because executeSql() is asynchronous function. So when I try to execute following line

clientData[i].projects[j].activities = result.rows;

it gives me error saying "Cannot read property 'projects' of undefined"

Code snippet

    for (var i = 0; i < clientData.length; i++) {
        for (var j = 0; j < clientData[i].projects.length; j++) {
            var getActivities = "SELECT * FROM Activity \n\
                                WHERE activityID \n\
                                in \n\
                    (" + clientData[i].projects[j].activityIds + ")";
            tx.executeSql(getActivities, [], function (tx, result) {
                clientData[i].projects[j].activities = result.rows;
                updateClientData(clientData);
            });
        }
    }