What are props and how do you validate them?

Props are custom attributes used to pass data from parent to child components:

export default {
  props: {
    // Basic syntax
    title: String,
    // With validation
    age: {
      type: Number,
      required: true,
      validator(value) {
        return value >= 0
      }
    },
    // With default value
    message: {
      type: String,
      default: 'Hello World'
    },
    // Array or object defaults must use factory function
    tags: {
      type: Array,
      default: () => []
    }
  }
}

Prop validation types:

• String, Number, Boolean, Array, Object, Date, Function, Symbol
• Custom constructor functions
• Array of types: [String, Number]