eiru_pos/src/store/modules/cart.js

const state = {
    cart: [],
    total: 0
}

const getters = {
    getCartItems(state) {
        return state.cart
    },
    isEmpty(state) {
        return state.cart.length !== 0
    }
}

const mutations = {
    addToCart(state, payload) {
        let finded = state.cart.find(item => item.id == payload.data.id)

        if (finded) {
            payload.data.qty = payload.data.qty + 1
        } else {
            state.cart = [payload.data, ...state.cart]
        }
    },
    calculateTotal(state) {
        let sum = 0

        state.cart.forEach(item => {
            sum = sum + (item.list_price * item.qty)
        })
        
        state.total = sum
    }
}

const actions = {
    addToCart({ commit }, payload) {
        commit('addToCart', payload)
        commit('calculateTotal')
    }
}

export default {
    state,
    getters,
    mutations,
    actions
}