Implementation principle of data response function in Vue documentation

Vue is a popular open source front-end framework that provides many functions that facilitate development, the most important of which is the data response mechanism. The data response mechanism is the core of Vue's two-way data binding and an important concept for developing Vue applications. This article will delve into the internal mechanism of Vue to implement data response.

Vue’s data response mechanism is implemented through Object.defineProperty. Object.defineProperty is a built-in function in JavaScript, mainly used to change the characteristics of properties. Different from the set and get functions in JavaScript, it can directly add properties to objects and assign some special properties to these properties. Vue uses Object.defineProperty to add getter and setter functions to objects to achieve data response.

At the same time, Vue treats the real data as data and the observer as watcher. In order to facilitate management, it also introduces an attribute dep. When an attribute in data is introduced into the view and a watcher instance is generated, the watcher will be added to dep, thus establishing the association between watcher and dep. When the data in data is changed, dep will be notified to call the watcher instance associated with it, and then call the callback function set before the watcher instance to achieve responsive updating of the data.

A simple code example is given below:

let data = { name: 'Vue' };
Object.defineProperty(data, 'name', {
    get() {
        console.log('get', data.name);
        return data.name;
    },
    set(newValue) {
        console.log('set', newValue);
        data.name = newValue;
    }
});

console.log(data.name);
data.name = 'React';
console.log(data.name);

In the above code, we added a property named name to the data object through Object.defineProperty and defined the property The get and set functions.

When console.log(data.name) is executed, the get function of the name attribute will be called and "get Vue" will be output.

When data.name = 'React' is executed, the set function of the name attribute will be called, "set React" will be output, and then "get React" will be output.

The above is the implementation principle of Vue to implement data response. Through the association between Object.defineProperty and dep, watcher, and data, as well as the implementation of getter and setter functions, Vue implements effective responsive data updates, making it more convenient and efficient for developers to process data.

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