Which method in vue does not trigger view update

Vue is a popular JavaScript framework that is often used to build dynamic and interactive web applications. The core of Vue is responsive data binding. Whenever the data changes, Vue will automatically re-render the view. However, some methods and components of Vue do not automatically trigger view updates, which may cause confusion in some special cases.

This article will introduce which methods in Vue do not trigger view updates and why this happens.

1. Object.defineProperty()

Object.defineProperty() is a native function of JavaScript that allows developers to define the properties of an object. Vue uses Object.defineProperty() to implement reactive data binding. When we define a new property, Vue will automatically track it. When the property is modified, Vue will detect its change and automatically trigger a view update.

However, if we modify the property descriptor of an existing property (such as changing the property's get function), this will not trigger a view update. This is because Vue only tracks property descriptors at object creation time, not at runtime. Therefore, if you modify the property descriptor of an existing property, Vue does not know that it has changed.

2. Array.prototype.push()

Vue will track changes in the array. When we use Array.prototype.push() to add new elements, Vue will automatically Changes to the array are detected and the view is re-rendered.

However, if we directly modify the length property of the array, such as Array.prototype.length=0, this will not trigger the change detection of the array. This is because Vue will only track operations that can be observed, and directly modifying the length property of an array is an unobservable operation.

3. Object.assign()

Object.assign() is a native function of JavaScript, which is used to assign the values ​​of all enumerable properties from one or more source objects are copied to the target objects. When we use Object.assign() to update object content, Vue does not automatically trigger view updates.

This is because Vue relies on changes in property descriptors to detect object changes, and using Object.assign() does not change the property descriptor. Therefore, if you want Vue to detect changes in the object, please use the Vue.set() or this.$set() method to manually set the object's properties.

4. v-once directive

The v-once directive tells Vue to render the element only once and no longer trigger view updates. This is useful in special cases, such as when rendering static text to avoid unnecessary performance overhead.

However, when using the v-once directive, Vue will no longer track any changes to the element, so it will not automatically update the view when the properties behind the element change. If you need to update content behind a v-once element, use other methods provided by Vue, such as computed properties or watchers.

Conclusion

Vue’s reactive data binding is one of its most important features. Vue automatically re-renders views by tracking data changes, which allows us to quickly build dynamic and interactive web applications. However, some methods and directives may impair Vue's responsiveness, and we need to use them with care.

This article introduces some Vue methods and instructions that will not trigger view updates, including Object.defineProperty(), Array.prototype.length, Object.assign(), v-once instructions, etc. Understanding these limitations will help us use the Vue framework better and reduce unnecessary errors.

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