Print JSON array in expected format - arrays

Question

This is the code to get the details from my table.
function listshops(callback)
{
var array=[3,4];/*shopId*/
async.each(array,function(dat,callback){
async.parallel([
function(callback){
client.connection.query('select * from shop where shopId=?',dat,function(err,data1){
callback(null,data1);
});
},
function (callback) {
client.connection.query('select * from image where shopId=?',dat,function(err,data2){
callback(null,data2);
});
}
],
function(err,data)
{
var result = data.reduce(function(prev, curr) { /*merging the array*/
return prev.concat(curr);
});
console.log(result);
});
});
}
I got an output like this:: http://i.stack.imgur.com/NVUAu.png
i want to print my result in the below format:
{
"shops": [
{
"shopId": "3",
"shopName": "1",
"address": "abc",
"contactNumber":"1234"
"images": [
{
"imageId": "1",
"shopId": "3",
"imageUrl": "aaa",
},
{
"imageId": "2",
"shopId": "3",
"imageUrl": "bbb",
},
]
},
{
"shopId": "4",
"shopName": "2",
"address": "bbb",
"contactNumber":"1234"
"images": [
{
"imageId": "3",
"shopId": "4",
"imageUrl": "ccc",
},
{
"imageId": "4",
"shopId": "4",
"imageUrl": "ddd",
},
]
},
]
I got the values but some confusions in fetching the values.

Answer 1

You have two nested async tasks here, parallel and each.
Parallel takes care of getting the shop information and the images for one shop and calls the final callback with a two element array that has the results for your tasks.
This is your final callback for parallel:
function(err,data)
{
var result = data.reduce(function(prev, curr) { /*merging the array*/
return prev.concat(curr);
});
console.log(result);
});
data should be a two element array, where element 0 is the shop, and element 1 are the images. You just concatenate these together. If you want your images in the desired format, you should do data[0].images = data[1] to add the images key to your shop.
That so far is for one shop. Then there is the outer each loop. You are currently not giving this a final callback and not doing anything with the result.
Something like this:
function listshops(callback)
{
var array=[3,4];/*shopId*/
async.each(array,function(dat,eachCallback){
async.parallel([
function(parallelCallback){
client.connection.query('select * from shop where shopId=?',dat,function(err,data1){
parallelCallback(null,data1);
});
},
function (parallelCallback) {
client.connection.query('select * from image where shopId=?',dat,function(err,data2){
parallelCallback(null,data2);
});
}
],
// this is the final callback for parallel
function(err,parallelResult)
{
// construct one shop
var shop = parallelResult[0];
shop.image = parallelResult[1];
// pass the shop info back as a result to each
eachCallBack(shop);
});
},
// this is the final callback for each
function(err, eachResult) {
// eachResult is an array with the shops returned from parallel callback
var result = {
shops: eachResult
}
return result
}
);
}
I couldn't test this, so don't consider it an exact solution, but an explanation. I renamed your variables for better understandability, you don't have to do that in your code. The key thing to keep in mind is that you have two nested tasks here, like a nested loop and you also have to deal with the results on two levels.