const products = [
    {id: 1, name: 'alex', price: 10},
    {id: 2, name: 'bob', price: 20},
    {id: 3, name: 'haha', price: 50}
]

const carts = [
    {id: 1, quantity: 2}
]

// 合并
const list = carts.map((item)=>{
    // 查找一个
    const p = products.find(i=>i.id===item.id)
    return {...item, ...p}
}) 
console.log('list', list)

// 计算总计
const total = list.reduce((total, product)=>{
    return total + product.price * product.quantity
}, 0)
console.log('total', total)