Array of objects, with individual properties in javascript

Question

I am trying to build an array of objects in javascript. Somehow I have not found the answer I am looking for anywhere. Yes I did search questions.

So a traditional object has properties obviously such as:

item being the object

item = new Object();

with properties and methods

item.name = "sword"; // "sword" being the string name of the object
item.buy = buy; //buy being a function to add said item

that's just great and I get that.

I get arrays too.

My question is, if I want say 20 of those objects, how could i make them in an array instead of making many objects

example, I know I can do this.

item1 = new Object();
item1.name = "sword";
item1.buy = buy;

item2 = new Object();
item2.name = "shield";
item2.buy = buy;

However, I would like to do something like this

item = new Array();
item[0].name = "sword";
item[0].buy = buy;

item[1].name = "shield";
item[1].buy = buy;

Maybe it's obvious, but I'm not getting what's wrong here.

When i attempt to call

item[0].buy();

I encounter the error "Uncaught TypeError: Object 0 has no method 'buy' " and item[0].name is undefined.

What am I doing wrong and how do I go about this?

ncwrch · Accepted Answer · 2013-10-28 00:22:43Z

4

My guess is that what you want is an array of objects:

var item = new Array();
item[0] = {};
item[0].name = "sword";
item[0].buy = function() { return this.name };
item[0].buy();
// -> "sword"

answered Oct 28, 2013 at 0:22

ncwrch

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1 Comment

Brit Cornwell Over a year ago

Thank you! I figured this out about 2 minutes after posting the question. I had thought that everything being an object, that array elements were as well but did not realize that they only are when initialized as such.

net.uk.sweet · Accepted Answer · 2013-10-28 00:22:39Z

2

// create a new array
var items = [];

// You can push objects onto the array as literals like this
items.push({
 name: "sword",
 buy: buy
});

// Or you can create the new object as you're doing currently    
var item = new Object();
item.name = "shield";
item.buy = buy;

// And push it onto the array as before
items.push(item);

// Now you can access each object by it's index in the array 
items[0].buy();
console.log(items[1].name); // "shield"

answered Oct 28, 2013 at 0:22

net.uk.sweet

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1 Comment

Brit Cornwell Over a year ago

This is also a good solution. I like my code to be as concise as possible though. Thanks for the input!

elclanrs · Accepted Answer · 2013-10-28 00:26:12Z

0

You can use literals like this:

var items = [{
  name: '1',
  buy: buy
}, {
  name: '2',
  buy: buy
}, {
  name: '3',
  buy: buy
}];

But I would consider using prototypes since buy is a shared method:

function Item(name) {
  this.name = name;
}

Item.prototype.buy = function() {
  ...
};

var items = [
  new Item('1'),
  new Item('2'),
  new Item('3')
];

items[1].buy();

answered Oct 28, 2013 at 0:26

elclanrs

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Comments

charlietfl · Accepted Answer · 2013-10-28 00:26:12Z

0

Can simplify the syntax down to:

var arr=[
    {name:'foo',age:49},
    {name:'GG', age:12},
    {name:'MMMM', age:16}
];

All depends what your overall goal is.

Using var xyz={} is same as writing out new Object() simlarly for [] to start a new array

answered Oct 28, 2013 at 0:26

charlietfl

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Comments

Guilherme Sehn · Accepted Answer · 2013-10-28 00:27:10Z

0

You can create a function called Item that will return an object with the name property, then use prototype to attach a method to it. Although JavaScript does not have classes, this will behave similar to it.

function Item(name) {
    this.name = name
}

Item.prototype.buy = function() {
    // your code to buy an item
    // you can access your item's name property here by using this.name
    alert("You bought the item " + this.name)
}

Then, you can instantiate this function and add the returned objects to an array:

var items = []
items.push(new Item('sword'))
items.push(new Item('shield'))
items[0].buy() // will buy the item "sword"
items[1].buy() // will but the item "shield"

answered Oct 28, 2013 at 0:27

Guilherme Sehn

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emran · Accepted Answer · 2013-10-28 00:29:59Z

0

looks as though you didn't add the items to your array via items.push(item1)

item1 = {};
item2 = {};

item1.name = "a";
item2.name = "b";

var buy = function() { console.log('buying... '+this.name); };

item1.buy = buy;
item2.buy = buy;

var items = [];

items.push(item1);
items.push(item2);
items[0].buy();

answered Oct 28, 2013 at 0:29

emran

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The Alpha · Accepted Answer · 2013-10-28 00:33:42Z

0

Because, you didn't create any object at the 0 index of your array and buy should be a function

item = new Array();
// create an object at 0/first index of array which is equivalent of new Object
item[0] = {};
// create property 'name' and assign value ("sword") to it
item[0].name = "sword";
// create another property and assign a function as it's value
// so buy is a method of the first object that is in in the item array
item[0].buy = function(){
    return 'buy called';
};
// call 'buy' method from the first object of item array
console.log(item[0].buy());

edited Oct 28, 2013 at 0:33

answered Oct 28, 2013 at 0:23

The Alpha

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