just use map

let m = {}
for(let i = 0; i< _arr.length; iPP){
    let t = _arr[i]
    if(!m[t.area]){
        m[t.area] = []
    }
    m[t.area].push(t.name)
}

let arr = []
for(let key in m){
    arr.push({ area: key, name: m[key] })
}

the idea of dealing with array and object data is very important, the general means is recursion, or with the help of the third variable to complete traversal, you can also use the principle of non-repetition of object key values to do a lot of things.