Azure Node.js应用服务-创建自定义承诺

Question

I am working on an Azure App Service (Mobile App) project with a Node.js backend.

I have multiple user levels and certain API methods should be off-limits to non-elevated users. Basically, I have 3 levels of user:

• Normal user
• Super user
• Internal user (employee)

I have built code that functions correctly to check a user's status and prevent the API method from being used. Because this code is in use across many of my API methods, I am trying to create a shared code module so that I do not have the same code repeated 20+ times throughout my API.

The problem I am running into is that I can't figure out how to correctly return a promise from my shared code that will resolve with a boolean value.

Here's an instance of what I'm trying to do (non-functional code):

module.exports = {
    isEmployee: function(req, next) {
        var context  = req.azureMobile;
        var user     = context.user;
        var username = user.id;
        var query    = {
            sql        : 'Exec usp_...',
            parameters : [ { name: '...', value: ... } ]
        };

        // The following line has compiler error
        return new Promise(function (fulfill, reject) {
            context.data.execute(query).then(function (results) {
                var result = results.Result;
                if (result === 'Success') {
                    fulfill(true);                  
                } else {
                    fulfill(false);                 
                }
            }).catch(next);         
        });     
    }
};

I got to this code by attempting to adapt code I found here .

I am getting a compiler error of "Cannot find name 'Promise'".

So, basically, I'm stuck on how to construct my own promise in this shared code method so that my other methods that call this method can await its running. I guess I'm trying to make this method "thenable". How can I do this on Azure Node.js?

Answer 1

Most probably, the version of V8 used by your nodejs version (intern the nodejs version itself) is not supporting the Promise constructor yet

Can you check the version of v8 used by the node version installed in the machine ?

you can do this using node -e 'console.log(process.versions.v8);' .

but in my opinion you should install npm module es6-promise and be done with it

install : npm install es6-promise

use : var Promise = require('es6-promise').Promise;

Answer 2

It seems you forget to install the Promise module in your mobile app.

You can simply use the Visual Studio Online "Monaco" (the online editor when you editing Easy APIs or Easy Tables). Click Open the Console button, run the command npm install promise --save to install the module in your mobile app and configure it into the package.json file.

Then you can create a shared script in the directory, and invoke it in the Easy APIs scripts. For the quick reference, I build a simple structure:

I create the shared script with promise functionality:

var Promise = require('promise');
exports = module.exports = function customP(context) {
    var query = {
        sql: 'SELECT * from TodoItem',
    };
    return new Promise(function (fulfill, reject) {
        context.data.execute(query).then(function (results) {
            if (results.length > 0) {
                fulfill(true);                  
            } else {
                fulfill(false);                 
            }
        })       
    });
}

And invoked in the Easy API script api/test.js :

var customP = require('../customP');
module.exports = {
    "get":function(req,res,next){
        customP(req.azureMobile).then(function(data){
            if(data){
                res.json("it's true");
            }else{
                res.json("it's false")
            }
        })
    }
}

Any further concern, please feel free to let me know.