How to iterate a loop in nodejs - node.js

Question

I have a json variable
var a = { Account: [ 'Name', 'Site', 'BillingState', 'Phone', 'Type', 'Owner.Alias' ],
Contact: [ 'Name1', 'Site1' ] }
and i am iterating loop like this
app.post('/', function (req, res) {
a = req.body.table_structure
b = createSelectQuery(a) res.send(b) // this return only "FROM CONTACT" })
Where i have created another function hoping i could in return get the desired string but the loop went async
function createSelectQuery(a){
var selectQuery = "Select "
var obj = JSON.parse(a);
for (var c in obj){
for (var d in obj[c]){
selectQuery += obj[c][d] + ', '
}
selectQuery = "FROM "+c
}
return selectQuery
}
I am expecting result "SELECT Name, .. etc from Account but getting
only FROM Account as output

Answer 1

Try this
function createSelectQuery(a){
var selectQuery = "Select ";
var obj = JSON.parse(a);
for (var c in obj) {
selectQuery += obj[c].join(", ") + " FROM " + c;
}
return selectQuery;
}

Answer 2

you need to use callback which will make your looping synchronous

Answer 3

I belive because in JSON file 'Account' is array and you try to loop in to it as if it was an object. Try :
function createSelectQuery(a){
var selectQuery = "Select "
var obj = JSON.parse(a);
for (var c in obj){
for (var d=0; d < obj[c].length; d++){
selectQuery += obj[c][d] + ', '
}
selectQuery = "FROM "+c
}
return selectQuery
}

Answer 4

Instead of loop, you can try join the string using arr.join() and then append the string with Object.keys. That will do the trick
var selectQuery = "Select ";
var a = { Account: [ 'Name', 'Site', 'BillingState', 'Phone', 'Type', 'Owner.Alias' ]};
var obj = a;
var arr = obj['Account'];
var joinStr = arr.join(',').toString();
selectQuery = selectQuery +" "+joinStr +" FROM "+Object.keys(a);
console.log(selectQuery);