Javascript Array key as variable

Question

I im building and array where my array key is from a variable like this:

var product_id = $('#product_id').val(); //22
var art = $('#article_id').val(); //229
var stk =  $('#stk').val(); //20
var elements = [];
elements [art] = stk;
console.log(elements);

This is the result

Array[229]
228:"20"
length:229
__proto__:Array[0]

As you see the result, it actually created 229 array key,

When I make a AJAX POST with that variable. It post all 229 array item to it.

option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:
option[]:20

It is possible I just want to post 1 key and value.

elements[229] = 20;

Not all the unused. Thanks!

Below is my ajax call

$.ajax({
            url: 'product/getprice',
            type: 'post',
            data: { product_id: product_id, option: element },
            dataType: 'text',
            beforeSend: function() {
            },
            complete: function() {

            },
            success: function(json) {

                json = JSON.parse(json);

             },
            error: function(xhr, ajaxOptions, thrownError) {
                alert(thrownError + "\r\n" + xhr.statusText + "\r\n" + xhr.responseText);
            }
        });

It would help a lot if you posted the code making the ajax call that sends the full array. — T.J. Crowder
– T.J. Crowder, Commented Nov 19, 2016 at 11:42

T.J. Crowder · Accepted Answer · 2016-11-19 11:43:42Z

4

The array you're creating is a sparse array (an array with lots of missing entries). It sounds like whatever it is that you're using to serialize the array doesn't handle sparse arrays the way you want it to, instead acting as though the array weren't sparse.

So that gives you two options at least:

Change the serialization code. Since you haven't shown it, we can't help you there.

or
Use an object instead of an array:
```
var elements = {}; // Note {}, not []
```
None of the other code you've shown has to change, but it's possible your serialization code may need to change if you do this.

answered Nov 19, 2016 at 11:43

T.J. Crowder

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2 Comments

aliasav Over a year ago

Using objects, OP can still access elements using the branket syntax, i.e. elements[229]. And the unnecessary sparse structure is eliminated

Shiro Over a year ago

I missed out the concept of objects, due to my background is more to PHP. So my mind is locked with arrays. Thanks for the idea!

Rajshekar Reddy · Accepted Answer · 2016-11-19 11:49:53Z

1

You need an Object not an Array.

Change your elements variable syntax to be an Object using { } ,

[ ] stands for an array.

So the only code change required is

var elements = {};

Arrays don't have a key value type structure. Object has.

When you do elements[229] you are actually creating array of size 229. Which is not what you want

edited Nov 19, 2016 at 11:49

answered Nov 19, 2016 at 11:43

Rajshekar Reddy

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1 Comment

T.J. Crowder Over a year ago

"Arrays don't have a key value type structure." Yes, they do. That's why the OP is seeing the behavior he's seeing. In fact, standard arrays in JavaScript aren't really arrays at all, just objects with special handling for a class of property names and length, which use Array.prototype as their prototype.

karman · Accepted Answer · 2016-11-19 11:43:28Z

0

Change it to this way.

 var elements = {};
elements [art] = stk;

answered Nov 19, 2016 at 11:43

karman

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