javascript中函数之外的获取数组值的问题？

Question

I have created an array which will store dynamic values coming from DB. When I print the array inside the transaction function it is printing. when I tried to print out side I didn't get the values. I have declared the array globally. what is the problem, my code is as follows;

function sendCategoryDetails() {

    var selected_category = $('#select-choice :selected').val();
    alert("control : " + selected_category);
    var mycoodinatesDetails;
    var myLocation = new Array();
    var db = window.sqlitePlugin.openDatabase({name: "MYDB"});

    db.transaction(function (tx) {
        tx.executeSql("select Location from Locationlog WHERE Category = '"+selected_category+"';", [], 
            function (tx, res) {
                for (var i = 0; i < res.rows.length; i++) {
                    myLocation[i] = res.rows.item(i).Location;
                }
                alert (myLocation +" length : "+ myLocation.length); // Values are printing 
            });
    });
    alert (myLocation +" length : "+ myLocation.length); // values are not getting, It showing the length is 0
}

Any suggestions?

Answer 1

tx.executeSql is an async function. The alert works within the function since that is the callback and the async processing has finished. The alert after the function is trigger before the function has finished, thus being undefined .

Solution: Do the work inside the callback or call another function with the array passed as a parameter and do the work there.