How to solve "[Vue warn]: Avoid mutating the defaultProps" error

How to solve the "[Vue warn]: Avoid mutating the defaultProps" error

When using Vue.js to develop projects, you may encounter an error named " [Vue warn]: Avoid mutating the defaultProps" error. This error usually occurs when a component uses Vue's default properties defaultProps and attempts to change the values ​​of these default properties inside the component. This article will introduce the causes of this error and provide solutions.

The defaultProps attribute of the Vue component is used to define the default property value of the component. These default property values ​​can be used directly inside the component without receiving them through props. However, in Vue 2.x versions, defaultProps are read-only and do not allow changes inside the component. This error is triggered when we try to modify the value of defaultProps inside the component.

For example, consider the following simple Vue component:

Vue.component('my-component', {
  template: '<div>{{ message }}</div>',
  defaultProps: {
    message: 'Hello, World!'
  },
  data() {
    return {
      message: this.message
    }
  },
  created() {
    this.message += '!!!';  // 尝试改变defaultProps的值
  }
});

In this example, we define a component named my-component, use a default attribute message, and set it The value is set to 'Hello, World!'. Then in the component's created lifecycle hook, we try to change the value of message, which will trigger the "[Vue warn]: Avoid mutating the defaultProps" error.

To solve this error, we can use one of the following two methods:

1. Use the computed attribute

The computed attribute is one of the Vue components An important feature is that it can perform calculations based on responsive data and automatically update when dependent data changes. Therefore, we can use the computed attribute instead of directly modifying the value of defaultProps. Here is the modified code example:

Vue.component('my-component', {
  template: '<div>{{ computedMessage }}</div>',
  defaultProps: {
    message: 'Hello, World!'
  },
  computed: {
    computedMessage() {
      return this.message + '!!!';
    }
  }
});

In this example, we use a computed property called computedMessage, which depends on the value of defaultProps message. By calculating the new property value inside the computed property and returning it to the template for use, we avoid directly modifying the value of defaultProps.

2. Use props attributes

Another solution is to convert defaultProps into props attributes and use the props attribute inside the component to receive the value. The advantage of this is that we can modify the value of the props attribute inside the component without triggering the "[Vue warn]: Avoid mutating the defaultProps" error. The following is a modified code example:

Vue.component('my-component', {
  template: '<div>{{ computedMessage }}</div>',
  props: {
    message: {
      type: String,
      default: 'Hello, World!'
    }
  },
  computed: {
    computedMessage() {
      return this.message + '!!!';
    }
  }
});

In this example, we converted defaultProps to props attributes and specified a default value. Inside the component, we still use the computed property to calculate new property values ​​and return them to the template for use. When using the parent component, we can also modify its value by binding the props attribute.

Summary

In a Vue.js development project, when encountering the "[Vue warn]: Avoid mutating the defaultProps" error, we can use the computed attribute or convert defaultProps to props attributes to solve. This can avoid directly modifying the value of defaultProps, thereby optimizing the performance and maintainability of the component. Hope this article helps you!

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