对象数组按元素分组？ [英] object array Group by an element?

问题描述

请参阅此示例： JsFiddle

<问题：我有以下 JSON数组

  y = [ {LngTrend：15，DblValue：10，DtmStamp：1358226000000}，
 {LngTrend：16，DblValue：92，DtmStamp：1358226000000}，
 { LngTrend：17，DblValue：45，DtmStamp：1358226000000}，
 {LngTrend：18，DblValue：87，DtmStamp：1358226000000}，
 
 
 {LngTrend：15，DblValue：10，DtmStamp：1358226060000}，
 {LngTrend：16，DblValue：87，DtmStamp：1358226060000}，
 {LngTrend：17，DblValue：45，DtmStamp：1358226060000}，
 {LngTrend：18，DblValue：92，DtmStamp：1358226060000}] 
  

我试图通过 DtmStamp 对这些对象进行分组这样的事情：

  x = [[1358226000000,10,92,45,87]，[1358226060000,10,87， 45,92]，.......] 
  

换句话说：

  x [0] [0] = y [0] .DtmStamp; 
 x [0] [1] = y [0] .LngTrend; 
 x [0] [2] = y [1] .LngTrend; 
 x [0] [3] = y [2] .LngTrend; 
 x [0] [4] = y [3] .LngTrend; 
  

不幸的是，它以我不想要的东西结束。

这是我到目前为止所尝试的：

  var dataTrendArray = []; 
 $ .each（x，function（index，value）{
 var trendArray = []; 
 if（index％4 == 0）{
 trendArray.push（x [index] .DtmStamp）; 
 for（var i = 0; i< 4; i ++）{
 index = eval（index + i）; 
 trendArray.push（x [index ] .DblValue）; 
} 
} 
 
 console.log（trendArray）; 
 dataTrendArray.push（trendArray）; 
}）; 
  

有人可以帮助我走上正确的道路吗？

解决方案

您可以将JavaScript对象用作类似于地图的键/值数据结构。属性名称将用作键，而属性值将用作值。这将允许您分组。

  var y = [
 {LngTrend：15，DblValue： 10，DtmStamp：1358226000000}，
 {LngTrend：16，DblValue：92，DtmStamp：1358226000000}，
 {LngTrend：17，DblValue：45， DtmStamp：1358226000000}，
 {LngTrend：18，DblValue：87，DtmStamp：1358226000000}，
 {LngTrend：15，DblValue：10，DtmStamp ：1358226060000}，
 {LngTrend：16，DblValue：87，DtmStamp：1358226060000}，
 {LngTrend：17，DblValue：45，DtmStamp： 1358226060000}，
 {LngTrend：18，DblValue：92，DtmStamp：1358226060000}，
]; 
 
 var x = {}; 
 
 for（var i = 0; i< y.length; ++ i）{
 var obj = y [i]; 
 
 //如果此DtmStamp的属性尚不存在，请创建
 if（x [obj.DtmStamp] === undefined）
x [obj.DtmStamp] = [ obj.DtmStamp]; //使用DtmStamp的第一个元素分配一个新数组。 
 
 // x将始终是与当前DtmStamp对应的数组。将当前值推送给它。 
 x [obj.DtmStamp] .push（obj.DblValue）; 
} 
 
 console.log（x）; // x现在是由DtmStamp分组的对象。您可以在此轻松将其重新转换为数组。 
  

Please see this example: JsFiddle

Question: I have the following JSON Array

y= [ {"LngTrend":15,"DblValue":10,"DtmStamp":1358226000000},     
{"LngTrend":16,"DblValue":92,"DtmStamp":1358226000000},    
{"LngTrend":17,"DblValue":45,"DtmStamp":1358226000000},
{"LngTrend":18,"DblValue":87,"DtmStamp":1358226000000},


{"LngTrend":15,"DblValue":10,"DtmStamp":1358226060000},
{"LngTrend":16,"DblValue":87,"DtmStamp":1358226060000},
{"LngTrend":17,"DblValue":45,"DtmStamp":1358226060000},
{"LngTrend":18,"DblValue":92,"DtmStamp":1358226060000} ]

I was trying to group these object by DtmStamp end up having something like this :

 x =  [[1358226000000,10,92,45,87],[1358226060000,10,87,45,92], .......]

In other words:

x[0][0] = y[0].DtmStamp ;
x[0][1] = y[0].LngTrend ;
x[0][2] = y[1].LngTrend ;
x[0][3] = y[2].LngTrend ; 
x[0][4] = y[3].LngTrend ;

Unfortunately, it ends with something I don't want.

Here is what I have tried so far:

   var dataTrendArray = [];
           $.each(x, function (index, value) {
                var trendArray = [];
                if (index % 4 == 0) {
                    trendArray.push(x[index].DtmStamp);
                    for (var i = 0; i < 4; i++) {
                        index = eval(index + i);
                        trendArray.push(x[index].DblValue);
                    }
                }

               console.log(trendArray) ;
                dataTrendArray.push(trendArray);
            });

Can someone help me get on the right path?

解决方案

You can leverage JavaScript objects as a key/value data structure similar to a map. The property name will serve as the key, while the property value will serve as the value. This will allow you to group.

var y = [
     {"LngTrend":15,"DblValue":10,"DtmStamp":1358226000000},     
     {"LngTrend":16,"DblValue":92,"DtmStamp":1358226000000},    
     {"LngTrend":17,"DblValue":45,"DtmStamp":1358226000000},
     {"LngTrend":18,"DblValue":87,"DtmStamp":1358226000000},
     {"LngTrend":15,"DblValue":10,"DtmStamp":1358226060000},
     {"LngTrend":16,"DblValue":87,"DtmStamp":1358226060000},
     {"LngTrend":17,"DblValue":45,"DtmStamp":1358226060000},
     {"LngTrend":18,"DblValue":92,"DtmStamp":1358226060000},
];

var x = {};

for (var i = 0; i < y.length; ++i) {
    var obj = y[i];

    //If a property for this DtmStamp does not exist yet, create
    if (x[obj.DtmStamp] === undefined)
        x[obj.DtmStamp] = [obj.DtmStamp]; //Assign a new array with the first element of DtmStamp.

    //x will always be the array corresponding to the current DtmStamp. Push a value the current value to it.
    x[obj.DtmStamp].push(obj.DblValue);
}

console.log(x); //x is now an object grouped by DtmStamp. You can easily turn it back into an array here.

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