Vue 数据劫持

function Observer(data) {
this.data = data;
this.walk(data);
}

Observer.prototype = {
walk: function(data) {
var me = this;
Object.keys(data).forEach(function(key) {
me.convert(key, data[key]);
});
},
convert: function(key, val) {
this.defineReactive(this.data, key, val);
},

defineReactive: function(data, key, val) {
    var dep = new Dep();
    var childObj = observe(val);

    Object.defineProperty(data, key, {
        enumerable: true, // 可枚举
        configurable: false, // 不能再define
        get: function() {
            if (Dep.target) {
                dep.depend();
            }
            return val;
        },
        set: function(newVal) {
            if (newVal === val) {
                return;
            }
            val = newVal;
            // 新的值是object的话，进行监听
            childObj = observe(newVal);
            // 通知订阅者
            dep.notify();
        }
    });
}

};

function observe(value, vm) {
if (!value || typeof value !== ‘object’) {
return;
}

return new Observer(value);

};

var uid = 0;

function Dep() {
this.id = uid++;
this.subs = [];
}

Dep.prototype = {
addSub: function(sub) {
this.subs.push(sub);
},

depend: function() {
    Dep.target.addDep(this);
},

removeSub: function(sub) {
    var index = this.subs.indexOf(sub);
    if (index != -1) {
        this.subs.splice(index, 1);
    }
},

notify: function() {
    this.subs.forEach(function(sub) {
        sub.update();
    });
}

};

Dep.target = null;