linq.js to group by array of objects in javascript -

i want use linq.js group following data date.

data2 = [{     "date": 1399298400.0,     "adid": 1057946139383,     "impressions": 1000000   }, {     "date": 1399298400.0,     "adid": 3301784671323,     "impressions": 535714   }...... etc. ];  

here's attempt:

var linq = enumerable.from(data2); data2 = linq.groupby(function (x) {   return x.date; }).select(function (x) {   return {     date: x.key(),     impressions: x.sum(function (y) {       return y.impressions | 0;     })   }; }).toarray(); 

however, it's not working correctly because sum of impressions before , after groupby close not identical.

what correct way use group in linq.js in case?

here's an example in fiddle full dataset here alerts total impressions before , after using groupby.

in order access key property of groupby, have within group method.

you can passing callback third parameter this:

var aggregatedobject = enumerable.from(dataarray)         .groupby("$.date", null,                  function (key, g) {                      return {                        date: key,                        impressions: g.sum("$.impressions | 0")                      }         })         .toarray(); 

the | 0 part of equation way of sanitizing data. in sample below, 1 of data array elements accidentally doesn't have impressions property. when javascript goes sum items in group, it'll chug along until encounters missing value, @ point result of entire aggregattion dreaded nan:

what pipe (|) operator in js return first value if exists, otherwise returns second one. expression safeguards against missing properties.

working demo stack snippets:

var dataarray = [{      "date": 1396828800,      "impressions": 100    }, {      "date": 1396828800,      "impressions": 250    }, {      "date": 1397001600,      "impressions": 300    }, {      "date": 1397001600      //,"impressions": 450  }];    var aggregatedobject = enumerable.from(dataarray)          .groupby("$.date", null,                   function (key, g) {                       return {                         date: key,                         impressions: g.sum("$.impressions | 0")                       }          })          .toarray();    console.table(aggregatedobject);

<script src="//cdnjs.cloudflare.com/ajax/libs/linq.js/2.2.0.2/linq.min.js"></script>

note: makes use of shorthand syntax, if prefer anytime see string dollar sign, can replace lambda syntax (the both same exact thing):

// lambda .select(function (x) { return x.impressions })  // shorthand .select("$.impressions") 

also, can find more info on linqjs group sum