The difference between computed and watch in vue

In Vue, computed is used to dynamically calculate values ​​based on other reactive data, while watch is used to trigger functions when specific reactive data changes.

The difference between computed and watch in Vue

In Vue, computed andwatch are all responsive features, used to handle changes in data. However, there are some key differences in their usage scenarios and functionality.

1. Purpose

• #computed: Computed properties are dynamically updated based on changes in other responsive data.
• watch: Listener that triggers a function when specific reactive data changes.

2. Data update

• computed: is always updated to the latest value and is calculated on access.
• watch: Triggered only when the data being listened to changes.

3. Calculation method

• computed: Calculated based on the defined getter function.
• watch: You can use custom callback functions or expressions to handle data changes.

4. Performance

• computed: Since it is calculated during access, the performance overhead is small.
• watch: Because it always listens for data changes, the performance overhead is large.

5. Dependencies

• computed: Computed properties can depend on other reactive data when the dependencies change Will be updated.
• watch: The listener can only listen to specific responsive data and does not rely on other data.

6. Usage scenarios

• computed: Suitable for scenarios where values ​​need to be dynamically calculated based on other responsive data, such as Calculate the total price based on the number of items in the shopping cart.
• watch: Suitable for scenarios where you need to react to specific data changes, such as validating a form when user input changes.

Simply put, computed is used to dynamically calculate values ​​based on changes in other reactive data, while watch is used when specific reactive data occurs Trigger function on change.

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