Component to parent events:

Sequence:

1. Component's button @click...
2. ...calls component’s addToCart method...
3. ...which emits add-to-cart event...
4. ...which triggers updateCart method in Vue instance

html:

<product @add-to-cart=“updateCart”></product>

component:

Vue.component(‘product’,{
    methods: {
        addToCart: function() {
            this.$emit(‘add-to-cart’)
        }
    },

    template: `
        <button @click=“addToCart”>Add to cart</button>
    `
}

Vue instance:

methods: {
    updateCart() {
        this.cart += 1;
    }
}