filter by property in child array using underscore.js

Question

I have an array like the following:

var result=[{"id": 1, "details": [{"ah": 1.0, "dId": 11},{"ah": 2.0, "dId": 11}, {"ah": 2.0, "dId": 12}]}, {"id": 2, "details": [{"ah": 1.0, "dId": 11},{"ah": 2.0, "dId": 11}]}]

Now I would like to filter it by the Id and dId-properties using underscore.js, eg. giving me all details for id=1 and dId=11 and doing a sum of the ah-properties. So eg. filtering for id=1 and dId=11 should return 3.

I tried something like this: _.where(result, {id: 1, details.dId:11})

But I couldn't get it to work.

I created a fiddle: http://jsfiddle.net/j9Htk/

Any help is appreciated

thanks

Thomas

Gruff Bunny · Accepted Answer · 2014-02-07 14:32:16Z

3

First filter the results to get those that have a matching id (can handle more the one with the same id):

var filteredList = _.filter(result, function(value){
    return value.id == 1;
});

Now sum the sums of all the ahs:

var sum = _.reduce(filteredList , function(memo, value){

    // find all details that have a matching dId
    var details = _.filter(value.details, function(detail){ return detail.dId == 11; });

    // return the sum of all the found details
    return memo + _.reduce(details, function(memo2, detail){ return memo2 + detail.ah; }, 0);

}, 0);

answered Feb 7, 2014 at 14:32

Gruff Bunny

28k10 gold badges74 silver badges61 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

RRikesh · Accepted Answer · 2014-02-07 13:33:56Z

0

I'm a beginner at underscore, here's my try:

var result=[{"id": 1, "details": [{"ah": 1.0, "dId": 11},{"ah": 2.0, "dId": 11}, {"ah": 2.0, "dId": 12}]}, {"id": 2, "details": [{"ah": 1.0, "dId": 11},{"ah": 2.0, "dId": 11}]}];


function calculate( result, id, dId ){

      var sum = 0;
      _.each( result[id].details, function( detail ){
        if( detail.dId == dId ){
            sum += detail.ah;
        }
      });

      console.log( 'id: ' + id + ' sum: ' + sum );
}

calculate( result,1,11 );

answered Feb 7, 2014 at 13:33

RRikesh

14.5k5 gold badges55 silver badges74 bronze badges

Comments

Zoltan.Tamasi · Accepted Answer · 2014-02-07 15:45:26Z

0

function extractSumOfAhs(result, id, dId) {
  return _.reduce(
    _.pluck(
      _.where(
        _.flatten(
          _.pluck(
            _.where(
              result,
              { id: id }
            ),
            "details"
          )
        ),
        {dId: dId}
      ),
      "ah"
    ),
    function(a,b) { return a + b; }
  )
}

or with chain:

function extractSumOfAhs(result, id, dId) {
  return _.chain(result)
    .where({id : id})
    .pluck("details")
    .flatten()
    .where({dId : dId})
    .pluck("ah")
    .reduce(function(a, b) { return a + b;})
    .value()  
}

edited Feb 7, 2014 at 15:45

answered Feb 7, 2014 at 14:55

Zoltan.Tamasi

1,38913 silver badges27 bronze badges

Collectives™ on Stack Overflow

filter by property in child array using underscore.js

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest