vue use this in data code example

Example 1: how to access both child event param and parent param in vue

<template>
    <ul>
        <product v-for="product in products"
                 :product="product"
                 @add="addToChart" />
    </ul>
</template>

<script>
const Product = {
    props: ["product"],
    render(h) {
        return h("li", { on: { click: this.click } }, this.product);
    },
    methods: {
        click() {
            this.$emit("add", { product: this.product, quantity: 42 });
        }
    }
};

export default {
    data() {
        return {
            products: ["Foo", "Bar"]
        };
    },
    components: {
        Product
    },
    methods: {
        addToChart({ product, quantity }) {
            console.log(product, quantity);
        }
    }
}
</script>

Example 2: vuejs accessing props from data

data: function() {
  var theData = {
    somevar: this.messageId,
    // other object attributes
  }

  return theData;
}