node js callback
function processData (callback) {
fetchData(function (err, data) {
if (err) {
console.log("An error has occurred. Abort everything!");
return callback(err);
}
data += 1;
callback(null, data);
});
}
processData(function (err, data) {
if (err) {
console.err(err);
} else {
console.log("Data: " + data);
}
});