Vue3 responsive advanced usage of shallowReadonly

In modern front-end development, Vue3 provides a rich responsive API to help developers manage state and data more efficiently. in,shallowReadonly()It is a very useful tool for scenarios where partial read-only state is required. This article will introduce in detailshallowReadonly()How to use and its application scenarios.

1. Introduction

shallowReadonly()is a responsive API provided by Vue3, which is used to set the top-level properties of an object to read-only. andreadonlyThe difference is,shallowReadonlyIt will only affect the top-level properties of the object, and will not recursively make the properties inside the object read-only.

2. Use scenarios

shallowReadonly()Applicable to the following scenarios:

• The top-level attributes are unchanged but the internal attributes are variable: When your business requirements require the object's top-level properties to remain unchanged, but allow modification of internal nested objects or arrays.
• Performance optimization: Compared withreadonly�shallowReadonly()It only applies to top-level attributes, and the performance overhead is smaller.

3. Basic use

Here is a simple example showing how to useshallowReadonly()。

<script lang="ts" setup>
import { shallowReadonly } from 'vue';

const state = {
  name: 'Duck every day',
  profile: {
    age: 18,
    address: {
      city: 'Guangzhou',
    }
  }
};
const shallowState = shallowReadonly(state);

// This will throw an error because the top-level property is read-only = 'change every day duck';

// This is OK because the `profile` object is not set to read-only = 31; 

// Similarly, the `address` object can also be modified = 'Shenzhen';
</script>

4. Detailed explanation of functions

4.1 Top-level attributes read-only

shallowReadonly()The top-level properties of the object will be set to read-only, and any attempt to modify the top-level properties will throw an error.

 = 'change every day duck'; // Throw an error

4.2 Internal attributes are variable

Nested properties inside the object will not be affected and can be modified freely.

 = 31; // Normal modification = 'Shenzhen'; // Normal modification

V. Best practices and cases

5.1 Keep the top-level state stable

In some application scenarios, it may be necessary to ensure that the top-level state of the object remains unchanged, such as a global configuration object. useshallowReadonly()It can effectively prevent top-level attribute modifications caused by incorrect operations.

const config = shallowReadonly({
  apiEndpoint: '',
  timeout: 5000,
  options: {
    retry: true,
    retryCount: 3
  }
});

// Top-level properties cannot be modified = ''; // Throw an error
// Internal properties can be modified = false; // Normal modification

5.2 Dynamic form data

In dynamic forms, it may be necessary to ensure that the structure of the form (top level attributes) remains unchanged, but allow users to modify the form content (internal attributes).

const formData = shallowReadonly({
  fields: [
    { name: 'username', value: '' },
    { name: 'email', value: '' }
  ]
});

// Top-level properties cannot be modified = []; // Throw an error
// Internal properties can be modified[0].value = 'newUsername'; // Normal modification

6. Summary

shallowReadonly()It is a very practical responsive API in Vue3, suitable for scenarios where partial read-only state is required. By setting the top-level properties of the object to read-only, it can effectively prevent misoperation, while allowing free modification of internal properties, providing the dual advantages of flexibility and performance optimization. I hope this article can help you better understand and use itshallowReadonly(), improve your Vue3 development experience.

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