I'm stumped by the bug lurking on line 52 of my JavaScript code - it's been eluding me!

I've encountered an error in my appery.io app while using the following javascript code. The error message reads as follows:

6/25/2014 9:37:35 PM:   Script All_Users_Data: TypeError: Cannot read property '_id' of undefined ( @ 52 : 33 ) -> if (all_photo[i].the_user._id == id) {

I need assistance in debugging this issue. My objective is to retrieve data from 3 collections, synchronize them based on _id from a 'users' collection, and then display user profile information.

var all_users = eval(DatabaseUser.query('52895ecce4b056c5e94f34f9'));
var all_profiles = eval(Collection.query('52895ecce4b056c5e94f34f9', 'profile'));
var all_status = eval(Collection.query('52895ecce4b056c5e94f34f9', 'Status'));
var all_photo = eval(Collection.query('52895ecce4b056c5e94f34f9', 'photo'));

// loop through all users
for (var i=0;i<all_users.length;i++)
{
    // find user profile by id and add first name to current user item
    getProfile(all_users[i]._id, all_users[i]);
    // find user status by id and add last status to current user item 
    getstatus(all_users[i]._id, all_users[i]);
    getphoto(all_users[i]._id, all_users[i]);
}

// function that retrieves user profile by id and updates it
function getProfile(id,curUser)
{
    var found = false;
    for (var i = 0; i < all_profiles.length; i++) {
        // assign profile name to the user if user id matches profile id
        if (all_profiles[i].the_user._id == id)
        {
            curUser.firstName = all_profiles[i].firstName;
            curUser.university = all_profiles[i].university ;

            found = true;
        }
    }
    if (!found)
    {
        curUser.f_name = "";
    }
}

// function that retrieves user status by id and updates it
function getstatus(id, curUser) {
    var found = false;
    for (var i = 0; i < all_status.length; i++) {
        if (all_status[i].the_user._id == id) {
            curUser.status = all_status[i].status;
            found = true;
        }
    }
    if (!found) {
        curUser.status = "";
    }
}
function getphoto(id, curUser) {
    var found = false;
    for (var i = 0; i < all_photo.length; i++) {
        if (all_photo[i].the_user._id == id) {
            curUser.photo = all_photo[i].photo;
            found = true;
        }
    }
    if (!found) {
        curUser.photo = "";
    }
}

// return complete user data updated with status and first name
response.success(JSON.stringify(all_users), "application/json");

Answer №1

When encountering the statement:

all_photo[i].the_user

We are dealing with an undefined value, meaning it does not have any properties like _id, since undefined objects do not possess any properties.

Is this where the issue originates from?

--

Your browser console is a handy tool:

console.log(all_photo);

This will allow you to examine the object and its properties after executing an eval.

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