IE8 以下 不支援 Object.keys

新增下列程式來解決這個問題:

Object.keys = Object.keys || function(o) {

    var result = [];

    for(var name in o) {

        if (o.hasOwnProperty(name))

          result.push(name);

    }

    return result;

};

來源: http://whattheheadsaid.com/2010/10/a-safer-object-keys-compatibility-implementation