Question

我正在学习Meteor / Javascript并且有一个我似乎无法弄清楚的问题。这更像是一个2部分的问题。

我可以做我正在尝试使用Meteor Mongo并避免在Javascript中进行映射/缩减吗？

如何在Javascript中对下面提到的2D数组进行映射/缩小？（将是一个很好的学习例子）。

所以这是设置，我有一个Mongo集合，它有以下数据;

{
  "_id" : "oBPoZCLo9JFhZGdtL",
  "guest" : "Jin",
  "itemLikes" : 25,
}
{
  "guest" : "Jin",
  "itemLikes" : 32,
  "_id" : "xz7AgJv52e8QF6XuA"
}
{
  "guest" : "Jin",
  "itemLikes" : 20,
  "_id" : "XHkJoJEDyxX8w9Zmc"
}
{
  "guest" : "Jin",
  "itemLikes" : 39,
  "_id" : "LeN5Nqhgdn79MCbct"
}
{
  "guest" : "Jim",
  "itemLikes" : 17,
  "_id" : "iuhM6v4yySrEpgeaY"
}
{
  "guest" : "Lex",
  "itemLikes" : 20,
  "_id" : "ed6dmDMzXKJRaBxFM"
}
{
  "guest" : "Lex",
  "itemLikes" : 35,
  "_id" : "dTiY7nEx9yNXQTp49"
}
{
  "guest" : "Mel",
  "itemLikes" : 21,
  "_id" : "XRb7Yz84nEDJhpSQh"
}
{
  "guest" : "Mel",
  "itemLikes" : 17,
  "_id" : "KX9TSsWrJREQtaSNu"
}
{
  "guest" : "Nance",
  "itemLikes" : 39,
  "_id" : "rJRr2WdBaWXEurbWf"
}

这是我用来解析数据的Meteor方法调用;

  myFunctionName: function () {
    var guestLikesTotal = []
    _.reduce(_.map(MyCollection.find().fetch(), function(doc) {
              //map
              return [doc.guest, doc.itemLikes];
              //the map gives me ["Jin", 25] for example
            }), 
            function(memo, num){ 
              //reduce
              if (guestLikesTotal.length == 0) {
                guestLikesTotal.push(num);
              } else {
                var count = guestLikesTotal.length;
                for(var i=0;i<count;i++) {
                  if(guestLikesTotal[i][0] == num[0]) {
                    guestLikesTotal[i][1] += num[1];
                  } else {
                      // not sure what to put here
                    }
                  }
                  // this is wrong because its pushing items with the same "name" into the array
                  guestLikesTotal.push(num);
                };
                return memo+=1;
              }, 0);
  return guestLikesTotal;
}

我试图让guestLikesTotal看起来像这样;

[["Jin",116],["Jim",17],["Lex",55],["Nance",56]]

非常感谢对这2个问题的任何帮助。

Answer 1

在javascript中，如果您的集合在数组中，则可以执行此操作：

var arr2 = [];
data.reduce( function (a, current, index) {
  if (!arr2.hasOwnProperty(current.guest)) {
    arr2[current.guest] = 0;
  }
  arr2[current.guest] += current.itemLikes;
}, data[0]);

var desired_arr = [];
for(var i in arr2) {
  desired_arr.push([i, arr2[i]]);
}
console.log(desired_arr);

完全小提琴：http://jsfiddle.net/juvian/LDBsT/

Meteor / Mongo Map / Reduce 2D Array

1 个答案: