如何使用Javascript/underscorejs找到包含对象的数组的交集？

Question

我不知道如何找到这组数组的交集：

[
 [
  {"name":"product1","light":"1"},
  {"name":"product2","light":"2"},
  {"name":"product5","light":"5"},
  {"name":"product4","light":"4"}
 ],
 [
  {"name":"product2","light":"2"},
  {"name":"product3","light":"3"},
  {"name":"product4","light":"4"}
 ],[...more arrays with objects]
]

这只是示例数据，实际数据集合变化很大，但结构相同。我希望返回的交集看起来像这样（一个包含交集对象的单一数组）：

[
 {"name":"product2","light":"2"},
 {"name":"product4","light":"4"},
]

我曾经尝试过与LoDashjs和Underscorejs一起使用：

_.intersectionObjects = _.intersect = function(array) {
var slice = Array.prototype.slice; // added this line as a utility
var rest = slice.call(arguments, 1);
return _.filter(_.uniq(array), function(item) {
  return _.every(rest, function(other) {
    //return _.indexOf(other, item) >= 0;
    return _.any(other, function(element) { return _.isEqual(element, item); });
  });
});
};

我需要这个是因为我正在尝试使用knockoutjs创建一个标签系统。我有一个分类的标签按钮布局，点击后会写入到一个"filter"可观察数组中，现在唯一剩下的就是找到包含在此可观察数组中的过滤产品的交集。

请帮帮我，我已经连续两天在尝试解决这个问题，但缺乏javascript知识来解决它。提前谢谢！

- Marz

Answer 1

尝试添加apply方法：

  var myArr = [
    [
      {"name":"product1","light":"1"},
      {"name":"product2","light":"2"},
      {"name":"product5","light":"5"},
      {"name":"product4","light":"4"}
    ],
    [
      {"name":"product2","light":"2"},
      {"name":"product3","light":"3"},
      {"name":"product4","light":"4"}
    ]
  ]

  _.intersectionObjects = _.intersect = function(array) {
    var slice = Array.prototype.slice;
    var rest = slice.call(arguments, 1);
    return _.filter(_.uniq(array), function(item) {
      return _.every(rest, function(other) {
        return _.any(other, function(element) {
          return _.isEqual(element, item);
        });
      });
    });
  };

  var myIntersection = _.intersectionObjects.apply(_, myArr);

  for (var i = 0; i < myIntersection.length; i++) {
    console.log(myIntersection[i]);
  }

  // Sample Output:
  // Object {name: "product2", light: "2"}
  // Object {name: "product4", light: "4"}

- SeanPlusPlus

---

应用：https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Function/apply - WiredPrairie

Answer 2

这是我使用的一种方法，看起来效果很不错。

var arr1 = [{"id":"1"},{"id":"2"},{"id":"3"}];
var arr2 = [{"id":"1"},{"id":"3"}];

function match(item){
var isMatch = _.matcher(item);
var matches = _.filter(arr2, isMatch);
  return matches[0];
}

var matchArray = _.compact(_.map(arr1, function(val){ return match(val)}));

document.write(JSON.stringify(matchArray));

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

- Claytronicon

Answer 3

如果您仅比较对象本身，就很可能会遇到错误，因为这将返回false：

var o1 = {"foo":"bar"};
var o2 = {"foo":"bar"};
return o1 == o2;

你需要比较对象内的值，并根据这些值进行交集：

这里的JSFiddle可以实现你想要的功能。http://jsfiddle.net/turiyag/bWrQW/6/

function valueIntersect(a1, a2) {
    var aReturn = [];
    for(i1 in a1) {
        o1 = a1[i1];
        for (i2 in a2) {
            o2 = a2[i2];
            if(equals(o1,o2)) {
                aReturn.push(o1);
                break;
            }
        }
    }
    return aReturn;
}

function equals(o1, o2) {
    if (!o2 || o1.length != o2.length) {
        return false;
    }
    for (i in o1) {
        if (o1[i] !== o2[i]) {
            return false;
        }
    }
    return true;
};

- turiyag

Answer 4

根据https://lodash.com/docs#intersectionBy，

_.intersectionBy([数组], [迭代器=_.identity])

- Gidon Wise