What is the difference between computed and watch in vue?

Difference: The calculated attribute computed supports caching, and will be recalculated only when the dependent data changes; it does not support asynchronous, and it will be invalid when there are asynchronous operations in computed, and data changes cannot be monitored. The monitoring attribute watch does not support caching. If the data changes, the corresponding operation will be triggered directly; it supports asynchronous.

watch, as the name suggests, is used to monitor data changes. There are three sources of data that can be monitored: props, data, and data in computed; watch provides two parameters. (newValue, oldValue), the first parameter is the new value, and the second parameter saves the old value;

computed is used to process complex logical operations, and is mainly distinguished from the methods storage method; methods storage method, , computed stores the data values ​​that need to be processed; methods are called every time, computed has a caching mechanism, and is only executed when it changes, with better performance;

The difference between computer and watch in vue:

Computed attribute computed:

1. Supports caching. Only when the dependent data changes, will it be recalculated

2. Does not support asynchronous, when there are asynchronous operations in computed Invalid, unable to monitor data changes

3.computed attribute values ​​will be cached by default. Computed attributes are cached based on their responsive dependencies, which are calculated based on the data declared in data

4. If an attribute is calculated from other attributes, this attribute depends on other attributes, it is a many-to-one or one-to-one, generally use computed

5. If the computed attribute attribute If the value is a function, then the get method will be used by default; the return value of the function is the attribute value of the attribute; in computed, the attribute has a get and a set method. When the data changes, the set method is called.

Listening attribute watch:

1. Does not support caching, data changes will directly trigger corresponding operations;

2.watch supports asynchronous;

3. The listening function receives two parameters. The first parameter is the latest value; the second parameter is the value before input;

4. When an attribute changes, the corresponding operation needs to be performed; One-to-many;

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