weird rails-y findBy method in JS

findby.js

var myClassCollection = [];

var _MyClass = function(id, foo) {
  this.id  = id;
  this.foo = foo;

  // some sort of arbitrary storage thing
  this.collection[id] = this;
}

_MyClass.prototype.collection = myClassCollection;

var MyClass = new Proxy(_MyClass, {
  get: function(target, name) {
    var match = /^findBy_(.*)/.exec(name);
    if (match) {
      name = match[1];
      return function(query) {
        return this.prototype.collection.filter(function(item) {
          return item[name] == query;
        });
      }.bind(target);
    }
    return target[name];
  }
});

var instance = new MyClass(5, "bar");

console.log(MyClass.findBy_id(5));
console.log(MyClass.findBy_foo("bar"));