Javascript function returns undefined error

Question

In my Cordova android app i am using getDeviceId function to get the unique device id.

function getDeviceId(){
        var temp;   
        newid=cordova.require('org.apache.cordova.uuid.UniqueDeviceID');
            newid.getDeviceID(success,fail);
            function  success(uuid){
              //this works 
              alert("inside function"+uuid);
              temp=uuid;
            }
            function fail(err){
             // alert("error"+err);
             }
           return temp;
        }

And i am calling this function like this way

var deviceId=getDeviceId();
//undefined error
alert("from function"+deviceId);

I will get device-id successfully inside the function,but the return value will give undefined error.

Medet Tleukabiluly · Accepted Answer · 2015-07-31 05:52:57Z

2

Use promise!

Short answer:

function getDeviceId(success, fail){
    return cordova.require('org.apache.cordova.uuid.UniqueDeviceID').getDeviceID(success, fail);
}

Better answer:

function getDeviceId(){
    var temp; //assume this as cache, this must be outside of this function scope, but for the sake of example
    var defer = q.defer(); //or any other promise libraries
    if(!temp){
        var cordova = cordova.require('org.apache.cordova.uuid.UniqueDeviceID');
        cordova.getDeviceID(function(uuid){
            temp = uuid;
            defer.resolve(uuid); //or other api depend on library
         }, function(err){
            temp = null; //clear cache on errors
            defer.reject('Could not get device id');
         });
    } else {
        defer.resolve(temp);
    }
    return defer.promise; //or other api depend on library   
}

Specific answer to you:

function getDeviceId(success, fail){
    return cordova.require('org.apache.cordova.uuid.UniqueDeviceID').getDeviceID(success, fail);
}

and then

getDeviceId(function(uuid){
    console.log(uuid); //this might be object, so drill to specific field
    alert("from function" + uuid);
}, function(errorMessage){
    alert(errorMessage);
});

Advice:

Checkout greate article about promises in details

edited Jul 31, 2015 at 5:52

answered Jul 31, 2015 at 5:39

Medet Tleukabiluly

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4 Comments

Medet Tleukabiluly Over a year ago

no, you are returning var temp which is undefined, it will be defined when success callback called, but that temp returned immediately, so obviously it will be always undefined

Medet Tleukabiluly Over a year ago

you need to pass function to var deviceId=getDeviceId();

shamon shamsudeen Over a year ago

Your specfic answer work partially but the temp variable returns undefined error

Medet Tleukabiluly Over a year ago

Let us continue this discussion in chat.

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