将js对象转化为树形结构

// 转换前：
source = [{
            id: 1,
            pid: 0,
            name: 'body'
          }, {
            id: 2,
            pid: 1,
            name: 'title'
          }, {
            id: 3,
            pid: 2,
            name: 'div'
          }]
// 转换为: 
tree = [{
          id: 1,
          pid: 0,
          name: 'body',
          children: [{
            id: 2,
            pid: 1,
            name: 'title',
            children: [{
              id: 3,
              pid: 1,
              name: 'div'
            }]
          }
        }]

let source = [
      {
        id: 1,
        pid: 0,
        name: 'body'
      }, {
        id: 2,
        pid: 1,
        name: 'title'
      }, {
        id: 3,
        pid: 2,
        name: 'div'
      }
    ]
    function etree(arr) {
      for (let i = arr.length - 1; i > 0; i--) {
        if (arr[i].pid == arr[i - 1].id) {
          arr[i - 1]['children'] = arr.pop()
        }
      }
      return arr
    }
    console.log(etree(source));