synchronous sqlite transactions node

Question

synchronous sqlite transactions node

I installed sqlite3 with npm

npm install sqlite3 --save

I have written some basic functions that I would like to be performed synchronously rather then with async.

for instance I would like to get column names in one function and the row count in another.

I would like to simply return these values. currently I am using a callback like so

d.cinfo = function(table, callback){
    var o = {};
    db.each("PRAGMA table_info(" + table + ")", function(err, col){
        o[col.name] = col.type;
    }, function(){
        if(typeof callback == 'function') callback(o);
    });
}

d is an object which is later exposed however Id like to return the values

d.cinfo = function(table, callback){
    var o = {};
    db.each("PRAGMA table_info(" + table + ")", function(err, col){
        o[col.name] = col.type;
    }, function(){
        return o;
    });
}

is there a way I can achieve this. I found documentation saying it was possible but then I learned that it was outdated and im not sure its meant for the same api

I have implemented bluebird however Promise.promisifyAll(middleware) returns and error "Object # has no method .then() anyone know what im doing wrong

node.js
sqlite3

Answer 1

I've come across a problem like this and many others while using Express and it really drives me crazy where I just can't avoid callback hells.

Some of the possible solutions can be:

Using the same old event driven style. Instead of calling nested functions, emit events for them. But I'm assuming you wouldn't like that very much, but that atleast gets rid of the nested callbacks.
There's a npm module called bluebird that allows you to extend existing modules with promises. (Using promisifyAll). So promises will still trim down the code and you'll have much cleaner code than you had before using promises.
If you don't mind switching frameworks, you can try KoaJS that allows you to yield(fun stuff from ECS 6) functions using generator functions(another cool feature). You can have more reading about this here.

So the above code can be re-written like:

var rows = yield db.each() //or something like that

this is an amazing feature but the drawback is that you have to use unstable versions of node (0.11.x). We also faced some issues setting up https using 0.11.x and had to downgrade to 0.10.x (we're not using koa either)

If there are only a few places where you need to do such kind of stuff, I would recommend using bluebird, but if you're tired of having lots of callbacks in your code, better go for Koa, although I've already mentioned you the tradeoffs.