Small helper function that enables you to drop collections based on their name. Use with caution!

mongodb_dropCollection_helpers.js

function dropCollections (colName) {
    var collectionNames = db.getCollectionNames();
    for (var i=0,len=collectionNames.length; i<len; i++) {
        var collectionName = collectionNames[i];
        if(collectionName.indexOf(colName) == 0) {
            db[collectionName].drop();
        }
    }
}