required props does not work vue code example

Example 1: vue js default prop

props: {
  name: {
    type: String,
    default: 'John Doe'
  }
}

Example 2: vue js props

Vue.component('blog-post', {
  // camelCase in JavaScript
  props: ['postTitle'],
  template: '<h3>{{ postTitle }}</h3>'
})

<!-- kebab-case in HTML -->
<blog-post post-title="hello!"></blog-post>