对象数组按元素分组？

Question

请看这个例子:JsFiddle

问题:我有以下内容 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} ]

我试图将这些对象分组,DtmStamp最后得到这样的东西:

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

换一种说法:

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);
            });

有人能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

你应该使用哈希.哈希将允许您轻松索引所有DblValue值DtmStamp.这是一个完整的工作示例:

的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
    ]
}

如果要防止重复,可以通过添加if/then逻辑来实现indexOf().