Is there a way to retrieve an array generated within a JavaScript loop?

Question

Is there a way to retrieve an array generated within a JavaScript loop?

I've been working on retrieving column values from a database and storing them in an array, but I keep getting an empty array as the result.

function FetchData(query, db) {
var resultArray = new Array();
db.transaction(function(tx) {
    tx.executeSql(query, [], function(tx, rs) {
        var length = rs.rows.length;

        for (var i = 0; i < length; i++) {
            var row = rs.rows.item(i);
            resultArray.push({latitude : row['latitude']});
        }
    });

});
return resultArray;
}

Even though I can see the array being populated inside the for loop, it ends up empty when returned.

javascript arrays

Answer 1

Answer №1

Your code is utilizing asynchronous functions, meaning a direct return will not be effective. To handle this, you should implement a callback function.

function Select(query, db, callback) {
    var result = new Array();
    db.transaction(function(tx) {
        tx.executeSql(query, [], function(tx, rs) {
            var len = rs.rows.length;
            for (var i = 0; i < len; i++) {
                var row = rs.rows.item(i);
                result.push({latitude : row['latitude']});
            }
            callback(result);
        });
    });
}

Select(function(result) {
    // process the result here
})

Answer 2

Your code is utilizing asynchronous functions, meaning a direct return will not be effective. To handle this, you should implement a callback function.

function Select(query, db, callback) {
    var result = new Array();
    db.transaction(function(tx) {
        tx.executeSql(query, [], function(tx, rs) {
            var len = rs.rows.length;
            for (var i = 0; i < len; i++) {
                var row = rs.rows.item(i);
                result.push({latitude : row['latitude']});
            }
            callback(result);
        });
    });
}

Select(function(result) {
    // process the result here
})

Answer 3

Answer №2

From the details you provided, it appears that tx.executeSql operates asynchronously. In this scenario, your Select function should ideally utilize a Promise (alternatively known as a Future) to handle the outcome, or simply send the results back to the original caller.

Answer 4

From the details you provided, it appears that tx.executeSql operates asynchronously. In this scenario, your Select function should ideally utilize a Promise (alternatively known as a Future) to handle the outcome, or simply send the results back to the original caller.

Is there a way to retrieve an array generated within a JavaScript loop?

Answer №1

Answer №2

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