How can I use variables as part of field names in the MongoDB shell?

Question

How can I use variables as part of field names in the MongoDB shell?

javascript, mongo-shell, mongodb

Solution

you could try for the JS object:

var t = 10;
var doc = {};
doc["Test."+t] = 0;

or

var t = 10, doc = {};
doc["Test."+t] = 0;

Problem

How can I use variables as part of field names in the mongodb shell? I am trying to do the following: ``` > var site = "google.com"; > var y = 10; > var m = 5; // This fails (field names as concatenation): > db.test.update({ "domain" : site}, { $inc : {"counts.year."+y : 1, "counts.month."+m : 1}}, upsert=true); > Thu Apr 19 19:12:56 SyntaxError: missing : after property id (shell):1 // This works: > db.test.update({ "domain" : site}, { $inc : {"counts.year.10" : 1, "counts.month.5" : 1}}, upsert=true); ``` I guess the problem is in the way the JS object is created: for instance `var t = 10; doc = {t : 0};` works but `var t = 10; doc = {"Test."+t : 0}`; does not. How can I work around this? Thank you, /David

Original source

Accepted Answer

you could try for the JS object:

```
var t = 10;
var doc = {};
doc["Test."+t] = 0;
```

or

```
var t = 10, doc = {};
doc["Test."+t] = 0;
```