怎么取出数组对象某个属性值

let arr = [
{
    "companyPk":1,
    "pk":1,
    "role":"角色1"
},{
    "companyPk":2,
    "pk":2,
    "role":"角色2"
},{
    "companyPk":3,
    "pk":3,
    "role":"角色3"
}
]
let newArr = arr.map(item=>item.role)
let roles = newArr.join(',') //角色1，角色2，角色3