Question

Is there any way to use dynamic keys with the node-mongodb-native driver? By this I mean having a variable hold the key instead of using the key directly.

As in when one would normally do this:

db.createCollection('col', function(err, col){
    col.insert({'_id':'wak3ajakar00'});
}

to do this instead:

db.createCollection('col', function(err, col){
    var ID = '_id';
    col.insert({ID:'wak3ajakar00'});
}

When I run the latter code, I end up with a document in collection db.col with a key called ID in addition to a standardly created _id, as opposed to just a key _id with the value wak3ajakar00. This leads me to believe that it isn’t actually possible to do this directly.

Instead, I’m now just creating the document that I want to insert ahead of time as follows:

db.createCollection('col', function(err, col){
    var ID = 'wak3ajakar00';
    var key = '_id';
    insertion = {}
    insertion[key] = ID;
    col.insert(insertion);
}

This works exactly like I want it to, but I just wanted to know if there are any better ways to go about this. JavaScript, NodeJS, and MongoDB are all new to me, so I feel like I could easily be missing something. If not, are there any cleaner ways to write the above code in JavaScript?

Best, and thanks,
Sami

Answer 1

2020 Edit: Object literals can now be created in a couple of handy new ways:

You can now use a variable as a property name in an object literal by wrapping it in square brackets:

const ID = "_id";
col.insert({ [ID]: "wak3ajakar00" });

You can use the variable name as the property name, and the variable value as the property value in an object literal like this:

const _id = "wak3ajakar00";
col.insert({ _id });

---

Original Answer from 2011:

In object literal syntax, you cannot use a variable as the key name, only values. The way to do it, is the way you already discovered – create your object first, then add the property as a separate step using square bracket notation.

var obj = {};
var ID = "_id";
obj[ID] = "wak3ajakar00";