Question

请参阅此示例：JsFiddle

问题：我有以下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} ]

我试图通过DtmStamp对这些对象进行分组，最终得到类似的内容：

 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内容：

   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？

Answer 1

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];

    //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.

Answer 2

您应该使用hash。通过哈希，您可以轻松地将所有DblValue值编入索引DtmStamp。这是一个完整的工作示例：

jsFiddle

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 = {};

var i = 0;
while(i++ < y.length) {
    var key = y[i].DtmStamp.toString();
    if (typeof(x[key]) == "undefined") x[key] = [];
    x[key].push(y[i].DblValue);
}

alert(JSON.stringify(x));

关键是对要分组的值使用哈希值。

结果：

{
    "1358226060000": [
        92,
        45,
        87,
        10
    ],
    "1358226000000": [
        87,
        45,
        92,
        10
    ]
}

如果您想防止重复，可以将if/then逻辑与indexOf()一起添加。

Answer 3

即使代码未填充（trendArray），您的代码也会推送空index % 4 != 0 s。相反，使用这个：

var dataTrendArray = [];
for (var i = 0; i < x.length; i += 4) {
    var trendArray = [ x[i].DtmStamp ];
    for (var j = i, l = Math.max(i + 4, x.length); j < l; j++) {
        trendArray.push(x[j].DblValue);
    }
    // console.log(trendArray) ;
     dataTrendArray.push(trendArray);
}

但是，如果您只使用DtmStamp作为键将trendArrays分组到一个对象中，它可能会更合适：

var dataTrend = {};
for (var i=0; i<x.length; i++) {
    var key = x[i].DtmStamp;
    if (key in dataTrend)
        dataTrend[key].push(x[i].DblValue);
    else
        dataTrend[key] = [ x[i].DblValue ];
}

Answer 4

您可以构建一个由DtmStamp索引的稀疏数组。

var x = [];
$.each(y, function(i, obj) {
    var s = obj.DtmStamp;
    if(!x[s]) x[s] = [];
    x[s].push(obj.DblValue);
});

//x is now a sparse array, indexed by DtmStamp

这比对象更有优势，即数组元素的顺序为DtmStamp。

//To loop through x
for(i in x) {
    ...
}

Answer 5

 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 k in y){
  if(x[y[k]["DtmStamp"]] == undefined)
     x[y[k]["DtmStamp"]] = [];
     x[y[k]["DtmStamp"]].push(y[k]["DblValue"])
}
alert(JSON.stringify(x))
console.log(x);

请参阅http://plnkr.co/edit/511sKSdzHGYuvpYqKCPD?p=preview

对象数组按元素分组？

5 个答案: