examples-eval.rst

db.runCommand( {
      eval: function(name, incAmount) {
               var doc = db.myCollection.findOne( { name : name } );

               doc = doc || { name : name , num : 0 , total : 0 , avg : 0 };

               doc.num++;
               doc.total += incAmount;
               doc.avg = doc.total / doc.num;

               db.myCollection.save( doc );
               return doc;
            },
      args: [ "eliot", 5 ]
   }
);

db.eval( function(name, incAmount) {
            var doc = db.myCollection.findOne( { name : name } );

            doc = doc || { name : name , num : 0 , total : 0 , avg : 0 };

            doc.num++;
            doc.total += incAmount;
            doc.avg = doc.total / doc.num;

            db.myCollection.save( doc );
            return doc;
         },
         "eliot", 5 );