js 对象数据观察者实现

var observer = function (originalData) {
    var newData = {};
    newData.observer = {};
    newData.$data = {};
    for (var key in originalData) {
        (function (key) {
            newData.$data[key] = originalData[key];
            Object.defineProperty(newData, key, {
                set: function (val) {
                    newData.$data[key] = val;
                    this.dispatch(key, val);
                },
                get: function () {
                    return newData.$data[key];
                }
            });
            newData.observer[key] = [];
        })(key);
    }
    newData.on = function (key, callback) {
        newData.observer[key].push(callback);
    };
    newData.dispatch = function (key, val) {
        for (var i in newData.observer[key]) {
            newData.observer[key][i](val);
        }
    };
    return newData;
};
var data = observer({age: 1, name: 'mahuan'});

data.on('name', function (val) {
    console.log('hello, ' + val);
});
data.on('age', function (val) {
    console.log('oh, you are ' + val);
});
data.name = "mahuan";
data.age = 3;

hello, mahuan
oh, you are 3