How is data binding implemented in Vue?

Vue.js is a lightweight front-end framework often used to build single-page applications. One of its most acclaimed features is data binding. In Vue, you can directly bind data to a view, which allows the view to update accordingly when the data changes. So, how is data binding implemented in Vue? Below is a brief explanation of this process.

The core of implementing data binding is to detect changes. Vue achieves this by using a detector. The detector will first listen for data changes, and then notify the relevant views to update when there are changes. This process can be divided into three steps:

1. Dependency collection

The purpose of this step is to track which components depend on which data. In Vue, each component is an instance, and this instance is generated by a rendering function. The render function parses the component's template, and when a data binding is found in the template, it adds the binding to a dependency list. This dependency list records which data is used and which components use this data.

2. Data Hijacking

The purpose of this step is to track data changes. Vue uses the ES6 Proxy object to implement data hijacking. When we access data, Proxy will intercept the access operation and trigger the corresponding dependencies in the dependency collector. In this way, changes in data can be tracked.

3. View update

The purpose of this step is to reflect data changes to the view. In the dependency collector, Vue maintains a subscription list for each dependency. When data changes, the dependency collector notifies subscribing objects to tell them that the data has changed. Objects in the subscription list will receive this notification and trigger corresponding view updates. In this way, all data used on the component will be updated, thus achieving synchronization of data and views.

In addition to the above steps, Vue also provides some tools to help us achieve more flexible data binding. For example, the $watch method can monitor data changes and perform some custom operations when changes occur. We can also use computed to define computed properties to reduce unnecessary template rendering times.

To summarize, data binding in Vue is achieved through dependency collection, data hijacking and view updates. This process mainly relies on ES6's Proxy object, but also requires the use of many other technologies to achieve comprehensive data binding. With data binding, we can build large front-end applications more easily.

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