Understanding the Use of 'props' in Vue.js

The 'props' option in a Vue.js component is primarily used to receive data from parent components. Understanding this concept is fundamental when working with Vue.js, as it allows for the passing of data in a unidirectional downstream flow (from parent to child), making it easier to predict data flow in your application. A common example of this would be passing the name of a user from a 'UserContainer' component to a 'UserProfile' component.

In Vue.js, 'props' are custom attributes you can register on a component that allow you to pass data from a parent component down to its children components. Let's examine a practical example:

// Here's your parent component
Vue.component('parent-component', {
  template: '<child-component :user="parentUser"></child-component>',
  data: function() {
    return {
      parentUser: 'John Doe'
    }
  }
})

// And child component
Vue.component('child-component', {
  props: ['user'],
  template: '<p>{{ user }}</p>'
})

In this example, the 'parent-component' passes the 'parentUser' data down to the 'child-component' via the 'user' prop. Thus, you can use props to create more generic, reusable components that can be highly customized with different data inputs.

Best practices suggest that you should always use props to pass data from parent to child components. Updates to your application are therefore easier to track and debug, as they follow a logical path. If you need to pass data the other way (from child to parent), use custom events instead.

Using 'props' for receiving data from parent components helps you create a well-structured, easily maintainable code base. They provide a clear and predictable data flow, which, coupled with Vue.js reactivity, allows your application to be responsive and dynamic.