object array Group by an element?

Question

Please see this example: JsFiddle

Question: I have the following JSON Array

y= [ {\"LngTrend\":15,\"DblValue\":10,\"DtmStamp\":13582260         


        

Answer 1

You should use a hash. A hash will allow you to easily index all of the DblValue values by DtmStamp. Here is a full working example:

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));

The key is to use a hash on the values you want to group by.

Result:

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

If you want to prevent duplicates, you can do so by adding if/then logic in conjunction with indexOf().