I have an array of event objects called events. Each event has markets, an array containing market objects. Inside here there is another array called outcomes, containing outcome objects.

I want to use Underscore.js or some other method to find all of the events which have markets which have outcomes which have a property named test.

I imagine this would be achieved using a series of filters but I didn't have much luck!

I have an array of event objects called events. Each event has markets, an array containing market objects. Inside here there is another array called outcomes, containing outcome objects.

I want to use Underscore.js or some other method to find all of the events which have markets which have outcomes which have a property named test.

I imagine this would be achieved using a series of filters but I didn't have much luck!

• javascript
• arrays
• object
• underscore.js

• Is there any inverse reference? I mean from outcome to market and so on. Because in this case you can just filter all the outcome objects those match your search and go backwards until the event, then clean up the array for unique elements. – fguillen Commented May 30, 2012 at 18:00
• Can you provide an example of this? – user1082754 Commented May 30, 2012 at 18:13

4 Answers 4

I think you can do this using the Underscore.js filter and some (aka "any") methods:

// filter where condition is true
_.filter(events, function(evt) {

    // return true where condition is true for any market
    return _.any(evt.markets, function(mkt) {

        // return true where any outcome has a "test" property defined
        return _.any(mkt.outcomes, function(outc) {
            return outc.test !== undefined ;
        });
    });
});

No need for Underscore, you could do this with native JS.

var events = [{markets:[{outcomes:[{test:x},...]},...]},...];
return events.filter(function(event) {
    return event.markets.some(function(market) {
        return market.outcomes.some(function(outcome) {
            return "test" in outcome;
        });
    });
});

Yet of course you could also use the corresponding underscore methods (filter/select and any/some).

Try this:

_.filter(events, function(me) { 
    return me.event && 
        me.event.market && me.event.market.outcome && 
        'test' in me.event.market.outcome
}); 

DEMO

var events = [
  {
    id: 'a',
    markets: [{
      outcomes: [{
        test: 'yo'
      }]
    }]
  },
  {
    id: 'b',
    markets: [{
      outcomes: [{
        untest: 'yo'
      }]
    }]
  },
  {
    id: 'c',
    markets: [{
      outcomes: [{
        notest: 'yo'
      }]
    }]
  },
  {
    id: 'd',
    markets: [{
      outcomes: [{
        test: 'yo'
      }]
    }]
  }
];

var matches = events.filter(function (event) {
  return event.markets.filter(function (market) {
    return market.outcomes.filter(function (outcome) {
      return outcome.hasOwnProperty('test');
    }).length;
  }).length;
});

matches.forEach(function (match) {
  document.writeln(match.id);
});

Here's how I would do it, without depending on a library:

var matches = events.filter(function (event) {
  return event.markets.filter(function (market) {
    return market.outcomes.filter(function (outcome) {
      return outcome.hasOwnProperty('test');
    }).length;
  }).length;
});