下划线、嵌套分组和生成 JSON答案

【问题标题】：Underscore, Nested Group By and Generate a JSON下划线、嵌套分组和生成 JSON
【发布时间】：2018-04-05 06:40:37
【问题描述】：

我有一个包含重复对象的数组，我正在尝试获取一个唯一列表，其中唯一性由对象属性的子集定义。例如，

当前 JSON 对象：

[{"x":6811,"y":15551,"a":"a"},
{"x":6811,"y":15551,"a":"b"},
{"x":6811,"y":15551,"a":"c"},
{"x":6811,"y":15552,"a":"c"},
{"x":6812,"y":15551,"a":"c"}]

如何按两个属性分组

最后的结果是

[{"x":6811,"y":15551,"a":["a","b","c"]},
{"x":6811,"y":15552,"a":["c"]},
{"x":6812,"y":15551,"a":["c"]}]

如何使用下划线使其唯一并生成合并“a”键

【问题讨论】：

香草js解决方案也可以吗？
你不需要下划线
另外，请分享您的尝试。

标签： javascript underscore.js underscore.js-templating underscore.string.js

【解决方案1】：

您可以使用groupBy 在x 和y 上创建复合键。然后，使用map 遍历分组数据。

var data = [{"x":6811,"y":15551,"a":"a"},{"x":6811,"y":15551,"a":"b"},{"x":6811,"y":15551,"a":"c"},{"x":6811,"y":15552,"a":"c"},{"x":6812,"y":15551,"a":"c"}]
var groups = _.groupBy(data, ({x,y}) => `${x}_${y}`);
var result = _.map(groups, o => ({...o[0], a : _.pluck(o,'a')}));
console.log(result);

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"&gt;&lt;/script&gt;

【讨论】：

【解决方案2】：

这是一个使用 reduce 和 Object.values 的 vanilla js 解决方案

var output = Object.values( arr.reduce( (acc, c) => {
  var {x,y} = c; 
  var key = JSON.stringify({x,y}); //create a key with both x and y
  if ( acc[ key ] ) 
  {
    acc[ key ].a.push(c.a); //if key is already set, then push the value in a
  }
  else
  {
     acc[ key ] = c; //else set c as value for this key
     acc[ key ].a = [acc[ key ].a];
  }
  return acc;
}  ,{}) );

演示

var arr = [{
    "x": 6811,
    "y": 15551,
    "a": "a"
  },
  {
    "x": 6811,
    "y": 15551,
    "a": "b"
  },
  {
    "x": 6811,
    "y": 15551,
    "a": "c"
  },
  {
    "x": 6811,
    "y": 15552,
    "a": "c"
  },
  {
    "x": 6812,
    "y": 15551,
    "a": "c"
  }
];

var output = Object.values(arr.reduce((acc, c) => {
  var {
    x,
    y
  } = c;
  var key = JSON.stringify({
    x,
    y
  }); //create a key with both x and y
  if (acc[key]) {
    acc[key].a.push(c.a); //if key is already set, then push the value in a
  } else {
    acc[key] = c; //else set c as value for this key
    acc[key].a = [acc[key].a];
  }
  return acc;
}, {}));

console.log( output );

【讨论】：