mvvm/js/mvvm.js

function MVVM(options){
	this.$options = options;
	var data = this._data = this.$options.data;
	var me = this;

	// 数据代理
	// 实现 vm.xxx -> vm._data.xxx
	Object.keys(data).forEach(function(key) {
		me._proxy(key);
	});

	observe(data, this);

	this.$compile = new Compile(options.el || document.body, this)
}

MVVM.prototype = {
	$watch: function(key, cb, options) {
		new Watcher(this, key, cb);
	},

	_proxy: function(key) {
		var me = this;
		Object.defineProperty(me, key, {
			configurable: true,
			enumerable: true,
			get: function proxyGetter() {
				return me._data[key];
			},
			set: function proxySetter(newVal) {
				me._data[key] = newVal;
			}
		});
	}
};