convert simple callbacks into async await - node.js

Question

I am finding it hard to convert this user controllers code to async await. Can someone please help and guide me how can i do it too. So that i can also change any callbacks into async await.
Also if someone can provide a good source so that i can read about async await and how to apply them properly.
const User = require("../models/user")
exports.getUserById = (req, res, next, id) => {
User.findById(id).exec((error, user) => {
if (error || !user) {
return res.status(400).json({
error: "No user was found in DB"
})
}
req.profile = user
next()
})
}
exports.getUser = (req, res) => {
req.profile.salt = undefined;
req.profile.encrypted_password = undefined;
return res.json(req.profile)
}
exports.getAllUsers = (req, res) => {
User.find().exec((error, users) => {
if (error || !users) {
return res.status(400).json({
error: "No users was found in DB"
})
}
return res.json(users)
})
}
exports.updateUser = (req, res) => {
User.findByIdAndUpdate(
{ _id: req.profile._id },
{ $set: req.body },
{ new: true, useFindAndModify: false },
(error, user) => {
if (error) {
return res.status(400).json({
error: "You are not authorized to update this info"
})
}
user.salt = undefined;
user.encrypted_password = undefined;
res.json(user)
}
)
}

Answer 1

It should look something like this:
const User = require("../models/user");
exports.getUserById = async (req, res, next, id) => {
let user = await User.findById(id);
try {
if (!user) {
return res.status(404).json({
error: "No user was found in DB"
});
}
req.profile = user;
next();
} catch (err) {
return res.status(500).json({
error: "Something went wrong"
});
}
};
exports.getUser = (req, res) => {
req.profile.salt = undefined;
req.profile.encrypted_password = undefined;
return res.json(req.profile);
};
exports.getAllUsers = async (req, res) => {
let users = await User.find();
try {
if (users.length < 1) {
return res.status(404).json({
error: "No users was found in DB"
});
}
return res.json(users);
} catch (err) {
return res.status(500).json({
error: "Something went wrong"
});
}
};
exports.updateUser = async (req, res) => {
try {
let user = await User.findByIdAndUpdate(
{ _id: req.profile._id },
{ $set: req.body },
{ new: true, useFindAndModify: false }
);
user.salt = undefined;
user.encrypted_password = undefined;
return res.json(user);
} catch (err) {
return res.status(400).json({
error: "You are not authorized to update this info"
});
}
};
You should send back 404 errors if you cant find any user in the database. 400 means bad request.

Answer 2

You can achieve what you are asking by wrapping the function with Promise. In your example, you should use the solution given by Ifaruki, because mongoose already supports promises.
function waitSeconds(seconds) {
return new Promise(res => {
setTimeout(() => {
res();
}, seconds * 1000)
})
}
async function foo() {
console.log("Hello");
await waitSeconds(5);
console.log("World");
}
Here you can learn more about async in javascript