javascript - ES5/6 merging arrays and objects

Question

[{a1:1},{a2:2},{a3:3}]
// 上面结构转成下面结构~！求教思路。
[{
  a1:1,
  level:[
    {
      a2:2,
      level:[
        {
          a3:3
        }
      ]
    }
  ]
}]

Answer 1

[{a1:1},{a2:2},{a3:3}]
.reverse()
.reduce((a,b) => {
    return b.level = [ a ],b
})

Answer 2

var arr = [{a1:1},{a2:2},{a3:3}] 

arr.reduce(function(pre,cur){
    pre.level = [cur]
    return pre.level[0]
})

var result = [arr[0]]

console.log(JSON.stringify(result))

Answer 3

JSON.stringify([{a1:1},{a2:2},{a3:3}].reduce((a,b)=>{
    let c = a
    while(c.level){
        c = c.level[0]
    }
    c.level = [b]
    return a
}))