How to Loop Data and Validate in Mongodb - node.js

Question

I have a dynamic input field where user can add multiple category at once. Data sent at backend is like
['ELECTRONIC','TOYS','GAMES']
Now I want to check for each element of the array ,if they are already present on mongodb . If its present i want to store it in errors object as
errors={ 0: 'Duplicate Data found'}
I am attaching my code for validation which is not working please help . .
const Category = require('../../models/Category');
const fieldCheck = (req, res, next) => {
const data = req.body;
const errors = [];
for( i = 0; i < data.length ; i++){
Category.findOne({ category_name : data[i]})
.then(user => {
if(user){
// # If a reqistered User ID is found ,then move ahead
errors[i] = 'Duplicate Entry Found';
errors.push(errors[i]);
}
}).catch(err =>{
return res.json(err);
}
)
}
console.log(errors);
};
module.exports = fieldCheck;
My Category Schema is ....
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const categorySchema = new Schema ({
category_name:{
type:String,
unique:true,
isRequired:true,
},
date:{
type:Date,
default:Date.now()
}
});
module.exports = mongoose.model('Category',categorySchema);

Answer 1

You are trying to call an asynchronous method (findOne) inside a synchronous loop (for). As you experience, this is like oil and water.
An easy fix is to make your method asynchronous and use the await keyword, example:
const fieldCheck = async (req, res, next) => {
const data = req.body;
const errors = [];
try {
for( i = 0; i < data.length ; i++) {
let user = await Category.findOne({ category_name : data[i]});
if (user) {
// # If a reqistered User ID is found ,then move ahead
errors[i] = 'Duplicate Entry Found';
errors.push(errors[i]);
}
}
// I assume you wanted to respond to res.json here?
console.log(errors);
} catch (err) {
return res.json(err);
}
};
module.exports = fieldCheck;