Javascript 对象数组 按元素分组？
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object array Group by an element?
提问by Mina Gabriel
Please see this example: JsFiddle
请看这个例子：JsFiddle
Question: I have the following JSON Array
问题：我有以下几点 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 DtmStampend up having something like this :
我试图通过DtmStamp最终得到这样的东西来对这些对象进行分组：
x = [[1358226000000,10,92,45,87],[1358226060000,10,87,45,92], .......]
In other words:
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 ;
Unfortunately, it ends with something I don't want.
不幸的是，它以我不想要的东西结束。
Here is what I have tried so far:
这是我迄今为止尝试过的：
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);
});
Can someone help me get on the right path?
有人可以帮助我走上正确的道路吗？
回答by crush
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.
您可以将 JavaScript 对象用作类似于地图的键/值数据结构。属性名称将作为键，而属性值将作为值。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.
回答by Elliot B.
You should use a hash. A hash will allow you to easily index all of the DblValuevalues by DtmStamp. Here is a full working example:
您应该使用hash。散列将允许您轻松地按 索引所有DblValue值DtmStamp。这是一个完整的工作示例：
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));
The key is to use a hash on the values you want to group by.
关键是对要分组的值使用散列。
Result:
结果：
{
"1358226060000": [
92,
45,
87,
10
],
"1358226000000": [
87,
45,
92,
10
]
}
If you want to prevent duplicates, you can do so by adding if/thenlogic in conjunction with indexOf().
如果您想防止重复，您可以通过添加if/then与indexOf().
回答by Bergi
Your code pushes empty trendArrays even if they are not filled (index % 4 != 0). Instead, use this:
trendArray即使它们未填充 ( index % 4 != 0)，您的代码也会推送空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);
}
However, it might fit better if you just grouped the trendArrays into an object, using the DtmStampas keys:
但是，如果您只是使用DtmStampas 键将趋势数组分组到一个对象中，它可能更适合：
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 ];
}
回答by Beetroot-Beetroot
You can build a sparse array, indexed by DtmStamp.
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
This has the advantage over an object, that the array elements are in DtmStamp order.
这比对象具有优势，即数组元素按 DtmStamp 顺序排列。
//To loop through x
for(i in x) {
...
}
回答by user3772857
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);
