A simple implementation of vue.

How to use

1. Use npm i to install the dependent packages
2. Use webpack-server-dev to start a server used for devleoping
3. Open http://localhost:8080/
4. index.html shows the simplest version of Vue, including 3 core concepts Observer Dep Watcher. And index2.html shows a relatively complete version of Vue, except the 3 core concepts mentioned above, this version includes more functions: directives compile, and it shows how the code connect all these functions together.

Main code flow

1. Proxy this.xxx to this._data.xxx. this._data is an internal attribute.

2. Proxy this.$data to this._data.

3. Add watchers to all attributes of data, so any get/set action will be catched. And build the connection with Wathcer through Dep.

4. Dep is like a box that may contains many Wather instances.

5. Compile html according to el attribute. Find �all directives in the html, and create Directive instances for them. In each directive, it will also create watchers according to the attributes used in the directive.