Why aren't all fields written to an object in an array?

Question

Vue.js

Hi others!!
There is such a cart state file

import shop from '../../api/shop'
import * as types from '../mutation-types'

// initial state
// shape: [{ id, quantity, title, price }]
const state = {
    added: [],
    checkoutStatus: null,
}

// getters
const getters = {
    checkoutStatus: state => state.checkoutStatus
}

// actions
const actions = {
    checkout ({ commit, state }, products) {
        const savedCartItems = [...state.added]
        commit(types.CHECKOUT_REQUEST)
        shop.buyProducts(
            products,
            () => commit(types.CHECKOUT_SUCCESS),
            () => commit(types.CHECKOUT_FAILURE, { savedCartItems })
        )
    }
}

// mutations
const mutations = {
    [types.ADD_TO_CART] (state, { id, price }) {
        state.lastCheckout = null
        const record = state.added.find(p => p.id === id)
        if (!record) {
            state.added.push({
                id,
                price,
                quantity: 1
            })
        } else {
            record.quantity++
        }
    },

    [types.REMOVE_FROM_CART] (state, { id }) {
        state.lastCheckout = null
        const record = state.added.find(p => p.id === id)
        if (typeof record == 'object')
            var index = state.added.findIndex(p => p.id === id)
            if (state.added[index].quantity == 1) {
                state.added.splice(index, 1)
            } else {
                record.quantity--;
            }

    },

    [types.CHECKOUT_REQUEST] (state) {
        // clear cart
        state.added = []
        state.checkoutStatus = null
    },

    [types.CHECKOUT_SUCCESS] (state) {
        state.checkoutStatus = 'successful'
    },

    [types.CHECKOUT_FAILURE] (state, { savedCartItems }) {
        // rollback to the cart saved before sending the request
        state.added = savedCartItems
        state.checkoutStatus = 'failed'
    }
}

export default {
    state,
    getters,
    actions,
    mutations
}

why in the added array only objects with properties 'id' and 'quantity' are stored. I try to write 'price', I output the array to the console, but it is not defined? Guys help what is wrong.