JQuery removes empty arrays when sending

Question

I have the following code:

$.post('block_ajax.php'
    ,   {   'action': 'set_layout'
        ,   'listid': 123
        ,   'layout': []
        }
    ,   function(data) {
            // ...
        }
);

The recieving script (block_ajax.php) only recieves the "action" and "listid" parameters. When I inspect what is sent using Chrome, I see the "layout" parameter isn't even send to the backend script.

Since there is a difference between an empty array and the absence of an array, I'd like to have JQuery send the empty array. I can find some indications that JQuery (1.6.1) seems to do this, but not how to stop it from doing so. JSON format allows for empty arrays and empty objects, so I think it should be possible.

Does anybody know what to change so JQuery can send empty arrays?

Answer 1

Our organization has two approaches to the problem:

• Sending data as JSON as opposed to POST-data is a good all-purpose approach, though this is sometimes a little bit difficult to integrate with frameworks like Rails, because you may have to add explicit back-end calls to decode the JSON data.
• [""] as noted by vinod will work well, as many frameworks (e.g. Rails) will often treat this as an empty array. (for the reason, see this Stack Overflow answer).
  • Note: This works when trying to integrate with some aspects of Rails, specifically when sending a list of ids of objects that are related by a has_many relationship. E.g. if you have a foos table and a bars table, and foos has_many :bars through :foo_bars, a way to remove all associations on a foo object is to pass foo: { bar_ids: [""] }.

Both approaches are hackier than desired, and I would be glad to discover a cleaner approach.

Answer 2

2018, Sorry to answer old question, but here's a better answer IMHO:

var arr = [];

$.post('block_ajax.php', {
    'action': 'set_layout',
    'listid': 123,
    'layout': arr.toString() // It'll be empty string "" if array is empty, otherwise if array has value(s) it will be a string of comma-separated values
}, function(data) {
    // ...
});

Examples:

var layout = [].toString();// layout will be '' (empty string)
var layout = [1,2,3].toString();// layout will be string with comma-separated values '1,2,3' 

In back-end, whether it's empty string or comma-separated string, it will always be posted, just convert it to array.

Back-end (PHP example):

$layout = explode(',', $_POST['layout']);

Answer 3

i think json will help in such a case

encode the array in js and send the result then decode it in php

but this will take some resource

Answer 4

Try this:

(isset($_POST['layout'])) ? $_POST['layout'] : array();

to get a new empty array if the passed array is empty, the "real" array with data otherwise.

Answer 5

I solved this the following way, which I feel is easiest to read. Supposing there's an array myArray which could be populated or empty:

'requestParam': myArray.length === 0 ? '' : myArray

Even when empty, jQuery will not omit the requestParam argument.

Answer 6

I found a simple cheat that works

$.post('block_ajax.php'
    ,   {   'action': 'set_layout'
        ,   'listid': 123
        ,   'layout': [{}]
        }
    ,   function(data) {
            // ...
        }
);

Notice I defined the empty array as [{}]. The jQuery ajax command just sends an empty array without the empty object.

NOTE: [[]] does not work.

Answer 7

EDIT: See Luke's answer for a better solution: https://stackoverflow.com/a/31996181/827437

I've left my previous answer specific to how Rails handles [""] below, as the link above explains.

---

Note: Rails-specific

I am not sure why you need to send a blank parameter. Merely checking the existence of the parameter in the PHP script should be enough. However, if you really want to do it, use 'layout': [""] instead of 'layout': []. The parameter should be sent.

(In addition, you might want to rename layout to layout[] to indicate it's an array, but this is unnecessary.)