how to perform synchronously findOne & create With in foreach Loop? - node.js

Question

In the following code, I have an infinite loop which I don't know why it happens. My best guess is because the function inside is async the loop doesn't wait for it and so the loop never stops. What is the best way to solve this issue ?
for (var i = 0, len = studentsData.length; i < len; i++) {
// (function(i) {
// var p = new Promise(function(resolve, reject) {
// var item = studentsData[i];
// Find student
Student.findOne({
email: item.Email
},
function (err, student) {
if (err) {
reject(err);
} else {
if (!student) {
// Create Student.
var StudentObj = {
firstName: item.Name || null,
lastName: null,
contact: item.Mobile || null,
securityToken: UTIL.randomString(21),
email: item.Email
};
Student.create(StudentObj, function (err, newStudent) {
if (err) {
reject(err);
} else {
// return newStudent;
console.log("Student created with Id=", newStudent._id);
// resolve(newStudent);
}
});
}
}
}
);
//});
// studentPromise.push(p);
// })(i);
}**

Answer 1

Without know what studentsData variable is, I would say i is always less than studentsData.
You are making things very complicated for yourself, trying to run a callback function in a for loop like so.
I would be inclined to rewrite this using a promise and calling all the promises at once with promise.all
You could do something like this:
function findOrCreateStudent(item){
// push all promises into an array called promises
const promises = studentsData.map(async (studentData) => {
// first param is your query, second is the object of the new document you want to create
try {
return await Student.findOrCreate({email: item.Email}, studentData) // I'm assuming studentsData is an array of student objects you want to find or create
}catch(err){
console.log(`Unable to find or create studen ${err}`)
}
})
return Promise.all(promises) // call all promises
}