how to find specific string in key value pair in mongodb

i am having data in mongodb like that

[

{
  "name":"silvester",
  "product":"laptop,iphone,mobile,phone"
},

{
   "name":"john",
   "product":"cycle,bus,phone,laptop"
},

{
   "name":"franklin",
   "product":"cycle,phone"
}

]

How to find that laptop is in product key. if product key look like this 

{
"name":"XXX",
"product":"laptop"
}

I can easily find that name by using this db.collection.find("product":"laptop");

So how to find this?

Also let me know this three website name running under using backbone.js and node.js and mongodb technology such as www.trello.com . sorry for my worst english..

Using regex with mongodb

This worked for me

db.collection.find({"product": /laptop/})

Updated Answer

If you wish to use variables, try something like this:

var abc = "laptop";
// other stuff
userdetails.find({"product":new RegExp(abc)}).toArray(function(err,result){
  if (err) console.log ("error: "+err);
  else 
  {    
    // if you want the length
    console.log(result.length);
    // if you actually want to see the results
    for (var i = 0; i < result.length; i++)
    {
      console.log(result[i]);
    }
  }
});

Updated One More Time

var abc = "laptop";
// other stuff

// note this is case sensitive.  if abc = "Laptop", it will not find it
// to make it case insensitive, you'll need to edit the RegExp constructor
// to this: new RegExp("^"+abc+",|, "+abc+"(?!\w)", "i")

userdetails.find({"product":new RegExp("^"+abc+",|, "+abc+"(?!\w)")}).toArray(function(err,result){
  if (err) console.log ("error: "+err);
  else 
  {    
    // if you want the length
    console.log(result.length);
    // if you actually want to see the results
    for (var i = 0; i < result.length; i++)
    {
      console.log(result[i]);
    }
  }
});

regex will work perfectly fine. there is also good news for you as monogdb will be releasing full text search index in the upcoming version

http://docs.mongodb.org/manual/release-notes/2.4/#text-indexes