drupal_to_js() and anonymous functions

Question

I'm using the flot module to create some graphs in Drupal. Generally, it is working pretty well. However, I have come across an issue which is more general.

I am defining a settings array, which works for most things, but some flot settings allow for anonymous functions:

  xaxis: {
    transform: function (v) { return Math.log(v); },
    inverseTransform: function (v) { return Math.exp(v); }
  }

How could I encode this in PHP so that it will be output correctly? The flot module uses drupal_to_js(), and I can't put it outside of quotes as PHP will try to interpret it. If I put it inside quotes it will be treated as a string.

From my googleing it looks like json_encode() also doesn't support this.

A little more explanation: drupal_to_js() takes a PHP structure and transposes it to JavaScript.

  $top = array(
    'a_string' => 'A string will convert fine',
    'a_number' => 123 // as will a number,
    'an_array' => array('a' => 'nested arrays work fine too'),
  );

This will be transposed to something like

 [ a_string: 'A string will convert fine', a_number: 123 ...

I want to transpose a function; the following code will give me the string 'function (v) { return Math.log(v); }'.

  $top = array(
    'a_string' => 'function (v) { return Math.log(v); }',
  );

The following code will give me a PHP parse error (as it should be).

  $top = array(
    'a_string' => function (v) { return Math.log(v); },
  );

I want the text in the string to be used as a JavaScript literal, but I don't think it can be done.

Has anyone found a good way round this? I could output some raw JavaScript, but then I will lose a lot of functionality.

Answer 1

This guide can be used as a work around http://echodittolabs.org/blog/2011/04/setting-js-callbacks-drupal-json-and-some-jquery-sauce-jcarousel-controls

We are looking for a generalized solution to this here http://drupal.org/node/1148204

Answer 2

If I understand the problem correctly, you have two options here.

The first is to use drupal_add_js with the inline option set to true. drupal_to_js() deals specifically with transforming PHP variables into their JavaScript equivalent; in this case, you aren't dealing with variables, but rather with functions, so it's not a proper fit.

The second option (which I probably favor) is to not use anonymous functions at all. Instead, create your own JS file which looks something like this:

// Give yourself a namespace to play nice with other JS.
if ( !ProjectName.flot ) { ProjectName.flot = {}; }

ProjectName.flot.transform = function (v) {
  // …
}

ProjectName.flot.inverseTransform = function (v) {
  // …
}

From there, your code to call these functions would look more like:

xaxis: {
  transform: ProjectName.flot.transform(v),
  inverseTransform: ProjectName.flot.transform(v)
}

Which would still be added via drupal_add_js(). I prefer this method because maintaining your JS is a lot easier/more logical if it's in its own file. Either methods should work, though.