Setting array in javascript

Question

Noob question. Setting array elements throws an error.

I get this error when I run the script: array1[user_id] is undefined.

array1 = new Array();

// the data variable I got from a JSON source
// using jQuery
$.each(data, function(i, item) {

    // Set variables
    user_id = item.post.user_id;
    user = item.post.user;
    price = item.post.price;

    if (array1[user_id]['user'] != user) {
        array1[user_id]['price'] = price;
        array1[user_id]['user'] = user;
    }

}

It's not that bad, Cudos is clearly trying to define nested objects and doesn't realize each sub-object needs to be initialized independently. — Ruan Mendes
– Ruan Mendes, Commented Jun 11, 2011 at 0:44
@pst I am trying my best. I don't know about you but English is not my first language and javascript is pretty new to me. No reason to be rude. — Cudos
– Cudos, Commented Jun 11, 2011 at 0:48
@pst: did the OP not explain that the problem was that array1[user_id] is undefined? — Ruan Mendes
– Ruan Mendes, Commented Jun 11, 2011 at 1:00

Ruan Mendes · Accepted Answer · 2011-06-11 00:38:53Z

2

First, you should not use an array, if you need a hash map, use objects. In some languages, it's one thing, but in JS they're not.

When defining a nested object you have to define each level as an object.

var hash = {};

// the data variable I got from a JSON source
$.each(data, function(i, item) {

    // Set variables
    user_id = item.post.user_id;
    user = item.post.user;
    price = item.post.price;
    // Have to define the nested object
    if ( !hash[user_id] ) {
        hash[user_id] = {};
    }
    if (hash[user_id]['user'] != user) {
        hash[user_id]['price'] = price;
        hash[user_id]['user'] = user;
    }    
}

answered Jun 11, 2011 at 0:38

Ruan Mendes

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6 Comments

Ivan Over a year ago

Who said anything about jQuery?

Jared Farrish Over a year ago

@Ivan - Nobody, but it often times makes life eas(ier).

Ruan Mendes Over a year ago

@Ivan: the poster did, I just modified his original posting so it would work, I didn't add any jQuery. Read before you post and downvote!

Ivan Over a year ago

Ah, you're right. The poster should have mentioned it somewhere since I was thinking of a non-jquery solution.

Ruan Mendes Over a year ago

@Ivan: What was the poster supposed to mention? I also can't stand people that use jQuery for every answer, but the question is clearly not about jQuery, it just uses jQuery as part of the example.

|

pixelfreak · Accepted Answer · 2011-06-11 00:54:05Z

0

If I understand this question correctly, you have to initialize the first dimension of array1 first, like so:

array1[user_id] = {};

then you can do this:

array1[user_id]['user'] = 'whatever';

That is of course assuming your user_id is not undefined.

edited Jun 11, 2011 at 0:54

answered Jun 11, 2011 at 0:33

pixelfreak

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2 Comments

Cudos Over a year ago

Problem is that I don't know what the "user_id" variable is before I loop through the "data" variable.

Jared Farrish Over a year ago

Then I would use an object and try catch.

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