JS, JSON某个key值相同的放在一起

var a = [
  {
    name: '发如雪',
    age: 18
  },
  {
    name: '晴天',
    age: 19
  },
  {
     name: '白色风车',
     age: 19
  },
 {
     name: '一路向北',
     age: 22
  }
]
var b = {}
a.forEach(v=> {
  b[v.age]||(b[v.age]=[])
  b[v.age]&&b[v.age].push(v)
})
console.log(b)


{
        18: [
          {
            name: '发如雪',
            age: 18,
          }
        ],
        19: [
          {
            name: '晴天',
            age: 19,
          },
          {
            name: '白色风车',
            age: 19,
          }
        ],
        22: [
          {
            name: '一路向北',
            age: 22,
          }
        ]
      }