方法

let arr = [{name: 'AA', num: 2}, {name: 'bb', num: 1}, {name: 'cc', num: 2}, {name: 'AA', num: 55}, {name: 'bb', num: 2}, {name: 'AA', num: 1}]
let obj = {}
let data = []
let data2 = []
arr.map((item, index) => {
    if (!obj[item.name]) {
        obj[item.name] = true
        data.push(item)
    } else {
        data2.push(item)
    }
})
data.map(item => {
    data2.map(item2 => {
        if (item2.name === item.name) {
            item.num += item2.num
        }
    })
})
console.log(...data) // {name: "AA", num: 58} {name: "bb", num: 3} {name: "cc", num: 2}