Composition based database tool.

CDB.js

var DB = {};

DB.collections = {};

var Collection = function(Constructor, IndexInterface) {
  var d = []
    , i = new IndexInterface;

  return {

    add: function(data) {
      d.push(new Constructor(data));
      i.index(d.length - 1, data);
    },

    get: function(query) {
      return d[i.atIndex(query)];
    }

  };
};

var IdIndexer = function() {
  this.indexes = {};
};

IdIndexer.prototype.atIndex = function(query, col) {
  if(typeof query === 'number' ? query : query.id) {
    return this.indexes[query || query.id];
  } else {
    atIndex(query);
  }
};

IdIndexer.prototype.index = function(ind, data) {
  if(data.id) {
    this.indexes[data.id] = ind;
  } else {
    throw new Error("No id to index for data", data);
  }
};