Declare array of objects containing objects

Question

I have an array of objects that contain other objects. At the moment the way I declare them is pretty long winded. Is there are more condense way to do the following:

function city(name,population)
{
 this.name = name;
 this.population = population;
}

function state(name)
{
 this.name= name;
 this.cities = new Array();
}

function country(name)
{
 this.name= name;
 this.states = new Array();
}

Countries = new Array();
Countries[0] = new Country("USA");
Countries[0].states[0] = new State("NH");
Countries[0].states[0].cities[0] = new city("Concord",12345);
Countries[0].states[0].cities[1] = new city("Foo", 456);
...
Countries[3].states[6].cities[35] = new city("blah", 345);

Is there a way to declare this setup that isn't so verbose, something similair to how an xml would be layed out, something like:

data =
usa
  NH
     concord: 34253
     foo: 3423
     blah: 99523
  NC
     place: 23522
Uk
  foo
     bar: 35929
     yah: 3452

I can't figure out how to nest array declarations without having to constantly repeat the variable names.

Inserve · Accepted Answer · 2012-05-09 13:27:57Z

18

Use object and array literals:

var data = {
    usa : {
        NH : {
           concord: 34253,
           foo: 3423,
           blah: 99523
        },
        NC : {
           place: 23522
        }
    },
    uk : {
      foo : {
         bar: 35929,
         yah: 3452
      }
    }
}

Or something that reflects your original code more directly:

var Countries = [ 
    {
        name : 'USA',
        states : [
            {
                name : 'NH',
                cities : [
                    {
                        name : 'Concord',
                        population : 12345
                    },
                    {
                        name : "Foo",
                        population : 456
                    }
                    /* etc .. */
                ]
            }
        ]
    },
    {
        name : 'UK',
        states : [ /* etc... */ ]
    }
]

Note: In javascript, var foo = [] is exactly equivalent to (and the preferred way to write) var foo = new Array(). Also, var foo = {} is the same as var foo = new Object().

Note: Don't forget to add commas between separate sub-objects.

edited May 9, 2012 at 13:27

Inserve

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answered Aug 27, 2010 at 6:42

slebetman

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3 Comments

Themasterhimself Over a year ago

How do I copy the contents of this array into another independent array. When I do, New_Countries[1] = Countries[0], I guess the object reference is being copied and both point to the same object. Thanks.

slebetman Over a year ago

@Themasterhimself: For deep copy you need to do it recursively yourself. Write functions to iterate through arrays and objects and have them recursively call each other until you hit either a number or a string. Use for(var x in y) for objects and for (var x=0;x<y.length;x++) for arrays.

slebetman Over a year ago

@Themasterhimself: Some libraries may already implement deep copy methods/functions. It may be worth looking up jQuery or underscore. But it's not really hard to write one yourself.

syockit · Accepted Answer · 2010-08-27 06:49:22Z

4

Would this be good enough for you?

var data = [
  { name: "USA",
    states: [
      { name: "NH",
        cities: [
          { name: "concord", population: 34253 },
          { name: "foo", population: 3423 },
          { name: "blah", population: 99523 }
        ]
      },
      { name: "NC",
        cities: [
          { name: "place", population: 23522 }
        ]
      }
    ]
  },
  {
    name: "UK",
    states: [
      { name: "foo",
        cities: [
                  { name: "bar", population: 35929 },
                  { name: "yah", population: 3452 }
                ]
      }
    ]
  }
]

answered Aug 27, 2010 at 6:49

syockit

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Comments

Scott Evernden · Accepted Answer · 2010-08-27 06:43:46Z

3

data = {
 usa: {
   NH: {
     concord: 34253,
     foo: 3423,
     blah: 99845
   }
 uk: {
   foo: {
     bar: 3454,
     yah: 33457
   }
  }
}

}

answered Aug 27, 2010 at 6:43

Scott Evernden

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