using async await in node js? - node.js

Question

I am trying to implement async/await module. In function2 if user is not present i want to stop the execution there . i dont want to execute function 3, if user present , i want to execute function3
const function1() {
//code
return a
}
const function2= (a,email) => model.user.findOne({ email:email}).then((user) => {
if (!user) {
****// want to stop execution here****
} else {
//update details of user
}
return dealer;
});
const function 3 = function(dealer) {
//mail sending
};
exports.mailer = async(email,callback) => {
try {
var a =await function1();
var dealer =await function2(a,email); //stop execution here
var res = await function 3(dealer);
await callback(res);
}catch (err){
callback(err);
}
}

Answer 1

Returning a new Promise in function2 which resolves if a user is found, and rejects if not should achieve what you want I believe.
Something like this:
const function1 = () => {
return a
}
const function2 = (a, email) => {
return new Promise((resolve, reject) => {
model.user.findOne({
email: email
}).then((user) => {
if (!user) {
// want to stop execution here****
reject(new Error('Error Message'))
} else {
// update details of user
resolve(dealer)
}
})
})
}
const function3 = (dealer) => {
//mail sending
}
exports.mailer = async (email, callback) => {
try {
var a = await function1()
var dealer = await function2(a, email) // stop execution here
var res = await function3(dealer)
await callback(res)
} catch (err) {
callback(err)
}
}