What are Vue.js mixins and how are they used?

Mixins in Vue.js are a flexible way to distribute reusable functionalities across components. They allow you to define a piece of reusable code that can be included in multiple components. This is particularly useful for sharing common methods, data, or lifecycle hooks.

To create a mixin, you define an object with properties and methods, and then include it in your component.

const myMixin = {
  data() {
    return {
      sharedData: 'This data is shared across components'
    };
  },
  methods: {
    sharedMethod() {
      console.log('This is a shared method');
    }
  }
};
export default {
  mixins: [myMixin],
  mounted() {
    this.sharedMethod();
  }
};

In this example, the `myMixin` object provides a shared data property and method, which can be utilized in any Vue component that includes it. This encourages code reuse and cleaner components.