如何在Node.js中使用异步

Question

I am struct at one problem and not able to find the solution for the same, I am working on nodejs express framework, below i have put my existing code, i am struct like how i can call the functions async.

exports.allProperties = function(req, res){
    var categoryList = [];      
    Category.find({}, function(err, categories) {
        categories.forEach(function(category) {
            categoryList[category.id]=category;
        });
        getProperties(categoryList,req,res);
    }); 
}

function getProperties(categoryList,req,res){
    var propertyList = [];
    var usersIds = [];
    Property.find({},function(err, properties){
        properties.forEach(function(property) {
            propertyList.push(property);
            usersIds.push(property.user_id)
        });
        getUsers(categoryList,propertyList, usersIds,req,res);          
    });
}


function getUsers(categoryList,propertyList, usersIds,req,res){
    var usersList = [];
    User.find({'id':{ $in: usersIds }},function(err,users){
        users.forEach(function(user) {          
            usersList[user.id] = [];
            usersList[user.id]["first_name"] = user.first_name;
            usersList[user.id]["last_name"] = user.last_name;
            usersList[user.id]["mail"] = user.last_name;
            usersList[user.id]["contact_number"] = user.contact_number;
        });
        res.render('admin/allProperties.ejs', {
            error : req.flash("error"),
            success: req.flash("success"),
            categories: categoryList,
            userLists: usersList,
            properties: propertyList
        });
    }); 
}

Here i want to get all properties but property has category and Users so inside of properties call i have to call getProperties() and same from getProperties i have to call getUsers it is possible like below which i would like to achive.

var properties = Property.find({});

var categories = Category.find({});

var users = User.find({});

So i can all properties, categories and users in single line of code after this three i will managed code and generate proper response and return or render the view.

How i can achieve this ?

Answer 1

yes you can achieve this with help of Async-Await

exports.allProperties = async function (req, res) {
    let categoryList = [];
    let propertyList = [];
    let usersIds = [];
    let categories = await Category.find({});
    categories.forEach(function (category) {
        categoryList[category.id] = category;
    });

    let properties = await Property.find({});
    properties.forEach(function (property) {
        propertyList.push(property);
        usersIds.push(property.user_id)
    });


    let users = await User.find({ 'id': { $in: usersIds } });
    users.forEach(function (user) {
        usersList[user.id] = [];
        usersList[user.id]["first_name"] = user.first_name;
        usersList[user.id]["last_name"] = user.last_name;
        usersList[user.id]["mail"] = user.last_name;
        usersList[user.id]["contact_number"] = user.contact_number;
    });

    res.render('admin/allProperties.ejs', {
        error: req.flash("error"),
        success: req.flash("success"),
        categories: categoryList,
        userLists: usersList,
        properties: propertyList
    }); 
}