Create API in node js to get data with multiple queries with my sql - node.js

Question

I am new to node js. I am trying to develop API for getting items list by its category list. For that i have create a function to fetch all available active featured tags from table ( featured_tags ). After that featured tag list fetch i want to get items list from ( items ) table which belongs to that particular tag. Can anyone help me how to so that in node js. I am using mysql database.
i have done below things to fetch categories from table.
route.js file
this.app.get('/list_menu',async(request,response) =>{
var itemlist = '';
const featuretags = helper.getFeatureTag().then(function(featuredtags){
//console.log('test');
itemlist = helper.getitems(featuredtags);
});
response.status(200).json({
status:200,
message: "success",
data:itemlist
});
});
function to get active featured tags in helper.js file
async getFeatureTag(){
return this.db.query("select * from featured_tags where status = 1 order by id desc ");
//const featuredtags = await this.db.query("select * from featured_tags where status = 1 order by id desc ");
}
Function which get items list of featured tags in helper.js file
async getitems(featuredtags){
var itemdata = [];
var featured_tagdataset = [];
if(featuredtags.length > 0){
for (var i = 0; i < featuredtags.length; i++) {
var row = featuredtags[i];
var featurtag = {};
featurtag.id = row.id;
featurtag.featured_tag = row.featured_tag;
var itemresult = await this.db.query("SELECT * FROM `items` WHERE status = 1 and FIND_IN_SET('"+ row.id +"' ,featured_tags) > 0");
if(itemresult.length > 0){
for(var l=0; l < itemresult.length; l++){
var itemrow = itemresult[l];
var item = {};
item.id = itemrow.id;
item.category_id = row.id;
item.name = itemrow.item_name;
itemdata.push(JSON.stringify(item));
}
}
featurtag.tag_items = itemdata;
featured_tagdataset.push(featurtag);
}
//console.log(featured_tagdataset);
return featured_tagdataset;
}else{
return null;
}
}
when i console featuredtag_dataset array in itemlist() in helper.js file it show me perfect response which i have to pass in API response. But in route.js it shows me blank in data parameter.
Can anyone help me for how to develop this type of APIs in node js.

Answer 1

This is because helper.getitems(featuredtags) method is called successfully but send response doesn't wait until method returns a response as node js is asynchronous .
you need to write the code in such a way that it should work in series. I have created sample example you can try this.
this.app.get('/list_menu',async(request,response) =>{
helper.getFeatureTag().then(function(featuredtags){
helper.getitems(featuredtags).then(function(itemlist){
response.status(200).json({
status:200,
message: "success",
data:itemlist
});
})
}
});

Answer 2

You forget to use await in your roter.js on calling asynchronous function, just update your router to this
this.app.get('/list_menu',async(request,response) =>{
const featuredtags = await helper.getFeatureTag(),
itemlist = await helper.getitems(featuredtags);
response.status(200).json({
status:200,
message: "success",
data:itemlist
});
});

Answer 3

you can either nested callback function or async await function or chained promises using then.