NodeJS & SQL Server (Callback)

Question

Having troubling creating a callback.

Example:

var connection = new sql.Connection(config);

connection.connect().then(function() {
    var request = new sql.Request(connection); // or: var request = connection.request();
    request.query('SELECT TOP 1 EQUIPMENT_ID FROM T_EQUIPMENT', function(err, recordset) {
        console.dir(recordset);
    });

}).catch(function(err) {
    // ...
});

Using npm mssql:

I need to make sure I have this data prior to continuing my next task.

So lets say after this I have something like:

console.log("completed");

Because it is async, the "completed" will come first, then the query.

How do properly create a callback so that when it is completed then process the next task without having to "nest" within the request.

If it's not possible let me know, I just want to make sure I am doing best practices.

Thank you very much!

Jeff Musser · Accepted Answer · 2015-04-06 18:21:53Z

2

// This is the function you call to connect to SQL.
// You will call this function and pass it a function you want executed
// after this function is completed which is where you see fn() at the bottom
function connectToSQL(fn) {
    connection.connect().then(function() {
    var request = new sql.Request(connection); // or: var request = connection.request();
    request.query('SELECT TOP 1 EQUIPMENT_ID FROM T_EQUIPMENT', function(err, recordset) {
        console.dir(recordset);
    });
    fn();
}).catch(function(err) {
    // ...
});

// Calling the function using a callback
// The function you are sending the function is the logic that will be executed
// when the fn() is called in the connectToSQL function
connectToSQL(function() {
    console.log("completed");
});

answered Apr 6, 2015 at 18:21

Jeff Musser

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1 Comment

ADL Over a year ago

Slightly modified it.: request.query('SELECT TOP 1 EQUIPMENT_ID FROM T_EQUIPMENT', function (err, recordset) { //console.dir(); fn(recordset); connection.close(); }); THANK YOU!

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