Question

I have the following code snippet :

function getCheckListTaskWithId(id){

 var tempTask = db.readTransaction(function (tx) {

      tx.executeSql('SELECT * FROM checklisttasks where id=? ', [id], function (tx, results) {
      var len = results.rows.length;
      if(len>0){
        var task=results.rows.item(0);
        var temp= new CheckListTask(task.id,task.crud,task.name,task.status);
        alert(temp);

      }   
    });

  });

}

the function that I pass to the tx.execute method is a call back function. Now I wan to return temp var present in callback function, from getCheckListTaskWithId function.

How Do I do this?

Answer 1

I am assuming that the executions of db.readTransaction and tx.executeSql are asynchronous. So you cannot return the result from them, as you don’t know when they’ll finish. The solution is use an asynchronous callback yourself. Make the getCheckListTaskWithId take a callback function as an argument and call it when result it available.

function getCheckListTaskWithId(id, callback) {
    var tempTask = db.readTransaction(function (tx) {
        tx.executeSql('SELECT * FROM checklisttasks where id=? ', [id], function (tx, results) {
            var len = results.rows.length;
            if(len > 0) {
                var task=results.rows.item(0);
                var temp= new CheckListTask(task.id,task.crud,task.name,task.status);
                alert(temp);
                callback(temp);
            }   
        });
    });
}