how can I create my mongodb query based on the input from the user in node.js?

Question

Currently in my app I store different forum posts. Users can add new messages and create new posts. Other users - while displaying the content - can filter it so that they will not see the content uploaded by specific users that they blocked earlier.

Each user is represented as a combination of device_id and display_name.

When users are fetching content, they do a post query and include an array of previously blocked users:

"blockedUsers": (
{
    "device_id" = "XXX";
    "display_name" = XXX;
},
{
    "device_id" = "YYY";
    "display_name" = YYY;
}
)

Currently there's a possibility of adding content with some registered display_name or anonymously.

Right now I support only filtering users with some display_name:

if(blockedUsers) {
    var excludedUsernames = [];

    for(var i in blockedUsers) {
         excludedUsernames.push(blockedUsers[i]['display_name']);
    }

    query.$and.push({ 'display_name': { $nin: excludedUsernames } });
}

That works fine - when user is registered and has some display_name (that is different than anonymous) - I don't care about his device_id, all I care is to block him by his display_name.

But, when some anonymous users has been blocked before:

"blockedUsers": (
{
    "device_id" = "XXX";
    "display_name" = "anonymous"; //represents anonymous user
},
{
    "device_id" = "YYY";
    "display_name" = "anonymous"; //represents anonymous user
}
)

I need to exclude his posts by device_id and the display_name == anonymous. In that case when there's some device_id but contains display_name != anonymous - I don't want to block that.

I don't know how to update my query so that it covers the requirement from above, could you help me with that? Thanks!

I think your post hasn't been answered the first time you posted it because it's really hard to follow what you're asking. For the sake of clarification, using pseudo code, am I correct that what you're trying to solve is a query like: !((displayName IN arrayOfBlockedNames) OR (displayName == 'anonymous' AND device_id IN arrayOfBlockedDevices)). Am I correct? — Paul
– Paul, Commented Dec 12, 2016 at 15:41

user2345 · Accepted Answer · 2016-12-18 06:41:11Z

2

+50

If I understood well:

If user has a banned device_id, then block him
If user has a banned display_name, then block him

In that case, it does not really matter if he is anonymous or not.

let excludedUsernames, excludedDevices;

blockedUsers.forEach((e) => {
    excludedUsernames.puhs({ e["display_name"] });
    excludedDevices.push({ e["device_id"] });
});

query.$and.push({ 'display_name' : { $nin: excludedUsernames } });
query.$and.push({ 'device_id'    : { $nin: excludedDevices   } });

EDIT

query.$or.push({
    $and: [
        { 'device_id'    : { $nin: excludedDevices }},
        { 'display_name' : "anonymous" }
    ]
});
query.$or.push({ 'display_name' : { $nin: excludedUsernames } });

edited Dec 18, 2016 at 6:41

answered Dec 12, 2016 at 15:59

user2345

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5 Comments

user3766930 Over a year ago

yes, almost - one more thing - user can access my app with same device_id, but different display_names. Then I need to block a device_id only when display_name == anonymous.

user2345 Over a year ago

Edited my answer.

user3766930 Over a year ago

thanks for your help! I had to modify the code slightly, now it looks like this: excludedUsernames.push({display_name:e['display_name']}); excludedDevices.push({device_id:e['device_id']}); (before it was raising an error), however now I'm getting another error in line query.$or.push({ $and: [... - it says: TypeError: Cannot read property 'push' of undefined

user2345 Over a year ago

That is because your object query has no property $or. Where you first initialized it, you must have specified a $and property. Change it to $or.

user3766930 Over a year ago

thank you for your help, I found your answer really helpful! Currently I struggle with different problem, maybe you will be able to help me, I posted a question here stackoverflow.com/questions/41212600/…

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