javascriptのオブジェクトを短く書く Shorthand property names (オブジェクト初期化子)

https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Object_initializer
http://yutapon.hatenablog.com/entry/2015/06/04/150000

// 以下の２つは等しい
var a = 'foo', b = 42, c = {};
var o = {a, b, c};

var a = 'foo', b = 42, c = {};
var o = {a:a, b:b, c:c};