Selecting a specific value from an array of objects in javascript

Question

I have data that is an array of objects like this:

var cars = [ {"year": 2003, "make": "Toyota", "model": "Tercel"}
           , {"year": 2009, "make": "Toyota", "model": "Tercel"}
           , {"year": 1999, "make": "Honda", "model": "Civic"}
           , {"year": 2002, "make": "Honda", "model": "Civic"}
           , {"year": 2004, "make": "Honda", "model": "Civic"}
           , {"year": 2007, "make": "Honda", "model": "Accord"}
           ...
           ]

I want to pull out only the latest of each make and model, so that the selected array looks like:

var selectedCars = [ {"year": 2009, "make": "Toyota", "model": "Tercel"}
                   , {"year": 2004, "make": "Honda", "model": "Civic"}
                   , {"year": 2007, "make": "Honda", "model": "Accord"}
                   ]

I know that I can filter, e.g.:

var selectedCars = _.max(cars, function(d) { return d.year; })

but that returns a single object out of the entire array. I've also tried looping through a list of makes and models and selected just the max year, but I can't make that work.

Another option would be to nest the data via something like d3.nest() with make and model as keys, but then I'm not sure how to get back to my selectedCars goal.

Thanks!

groupBy make. Select the maximum object per group (via map). map the desired value. — user166390
– user166390, Commented Mar 18, 2013 at 23:26

Matt Dodge · Accepted Answer · 2013-03-18 23:31:08Z

2

Check out Underscore's groupBy function. You should be able to use that and chain it with map

_.map(
    _.groupBy(cars, function(car) {
        return car.make + car.model;
    }),
    function(years, makeModel) {
        return _.max(years, function(year) {
            return year.year;
        });
    }
)

JSFiddle

answered Mar 18, 2013 at 23:31

Matt Dodge

11.2k7 gold badges42 silver badges58 bronze badges

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

Comments

btevfik · Accepted Answer · 2013-03-19 00:24:05Z

1

you can do something like this

 var cars = [ {"year": 2003, "make": "Toyota", "model": "Tercel"}
       , {"year": 2009, "make": "Toyota", "model": "Tercel"}
       , {"year": 1999, "make": "Honda", "model": "Civic"}
       , {"year": 2002, "make": "Honda", "model": "Civic"}
       , {"year": 2004, "make": "Honda", "model": "Civic"}
       , {"year": 2007, "make": "Honda", "model": "Accord"}
       ]

var carGroup = _.groupBy(cars, 'make');
for (var property in carGroup) {
if (carGroup.hasOwnProperty(property)) {
    var selectedCar = _.max(carGroup[property], function(d) { return d.year; }) 
}
alert(JSON.stringify(selectedCar));
}

http://jsfiddle.net/btevfik/BEx5a/

answered Mar 19, 2013 at 0:24

btevfik

3,4413 gold badges30 silver badges40 bronze badges

Collectives™ on Stack Overflow

Selecting a specific value from an array of objects in javascript

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related