.. _zend.view.helpers.initial.headscript:

HeadScript Helper
-----------------

The *HTML* **<script>** element is used to either provide inline client-side scripting elements or link to a remote
resource containing client-side scripting code. The ``HeadScript`` helper allows you to manage both.

The ``HeadScript`` helper supports the following methods for setting and adding scripts:

- ``appendFile($src, $type = 'text/javascript', $attrs = array())``

- ``offsetSetFile($index, $src, $type = 'text/javascript', $attrs = array())``

- ``prependFile($src, $type = 'text/javascript', $attrs = array())``

- ``setFile($src, $type = 'text/javascript', $attrs = array())``

- ``appendScript($script, $type = 'text/javascript', $attrs = array())``

- ``offsetSetScript($index, $script, $type = 'text/javascript', $attrs = array())``

- ``prependScript($script, $type = 'text/javascript', $attrs = array())``

- ``setScript($script, $type = 'text/javascript', $attrs = array())``

In the case of the * ``File()`` methods, ``$src`` is the remote location of the script to load; this is usually in
the form of a *URL* or a path. For the * ``Script()`` methods, ``$script`` is the client-side scripting directives
you wish to use in the element.

.. note::

   **Setting Conditional Comments**

   ``HeadScript`` allows you to wrap the script tag in conditional comments, which allows you to hide it from
   specific browsers. To add the conditional tags, pass the conditional value as part of the ``$attrs`` parameter
   in the method calls.

   .. _zend.view.helpers.initial.headscript.conditional:

   .. rubric:: Headscript With Conditional Comments

   .. code-block:: php
      :linenos:

      // adding scripts
      $this->headScript()->appendFile(
          '/js/prototype.js',
          'text/javascript',
          array('conditional' => 'lt IE 7')
      );

.. note::

   **Preventing HTML style comments or CDATA wrapping of scripts**

   By default ``HeadScript`` will wrap scripts with HTML comments or it wraps scripts with XHTML cdata. This
   behavior can be problematic when you intend to use the script tag in an alternative way by setting the type to
   something other then 'text/javascript'. To prevent such escaping, pass an ``noescape`` with a value of true as
   part of the ``$attrs`` parameter in the method calls.

   .. _zend.view.helpers.initial.headscript.noescape:

   .. rubric:: Create an jQuery template with the headScript

   .. code-block:: php
      :linenos:

      // jquery template
      $template = '<div class="book">{{:title}}</div>';
      $this->headScript()->appendScript(
          $template,
          'text/x-jquery-tmpl',
          array('id='tmpl-book', 'noescape' => true)
      );


``HeadScript`` also allows capturing scripts; this can be useful if you want to create the client-side script
programmatically, and then place it elsewhere. The usage for this will be showed in an example below.

Finally, you can also use the ``headScript()`` method to quickly add script elements; the signature for this is
``headScript($mode = 'FILE', $spec, $placement = 'APPEND')``. The ``$mode`` is either 'FILE' or 'SCRIPT', depending
on if you're linking a script or defining one. ``$spec`` is either the script file to link or the script source
itself. ``$placement`` should be either 'APPEND', 'PREPEND', or 'SET'.

``HeadScript`` overrides each of ``append()``, ``offsetSet()``, ``prepend()``, and ``set()`` to enforce usage of
the special methods as listed above. Internally, it stores each item as a ``stdClass`` token, which it later
serializes using the ``itemToString()`` method. This allows you to perform checks on the items in the stack, and
optionally modify these items by simply modifying the object returned.

The ``HeadScript`` helper is a concrete implementation of the :ref:`Placeholder helper
<zend.view.helpers.initial.placeholder>`.

.. note::

   **Use InlineScript for HTML Body Scripts**

   ``HeadScript``'s sibling helper, :ref:`InlineScript <zend.view.helpers.initial.inlinescript>`, should be used
   when you wish to include scripts inline in the *HTML* **body**. Placing scripts at the end of your document is a
   good practice for speeding up delivery of your page, particularly when using 3rd party analytics scripts.

.. note::

   **Arbitrary Attributes are Disabled by Default**

   By default, ``HeadScript`` only will render **<script>** attributes that are blessed by the W3C. These include
   'type', 'charset', 'defer', 'language', and 'src'. However, some javascript frameworks, notably `Dojo`_, utilize
   custom attributes in order to modify behavior. To allow such attributes, you can enable them via the
   ``setAllowArbitraryAttributes()`` method:

   .. code-block:: php
      :linenos:

      $this->headScript()->setAllowArbitraryAttributes(true);

.. _zend.view.helpers.initial.headscript.basicusage:

.. rubric:: HeadScript Helper Basic Usage

You may specify a new script tag at any time. As noted above, these may be links to outside resource files or
scripts themselves.

.. code-block:: php
   :linenos:

   // adding scripts
   $this->headScript()->appendFile('/js/prototype.js')
                      ->appendScript($onloadScript);

Order is often important with client-side scripting; you may need to ensure that libraries are loaded in a specific
order due to dependencies each have; use the various append, prepend, and offsetSet directives to aid in this task:

.. code-block:: php
   :linenos:

   // Putting scripts in order

   // place at a particular offset to ensure loaded last
   $this->headScript()->offsetSetFile(100, '/js/myfuncs.js');

   // use scriptaculous effects (append uses next index, 101)
   $this->headScript()->appendFile('/js/scriptaculous.js');

   // but always have base prototype script load first:
   $this->headScript()->prependFile('/js/prototype.js');

When you're finally ready to output all scripts in your layout script, simply echo the helper:

.. code-block:: php
   :linenos:

   <?php echo $this->headScript() ?>

.. _zend.view.helpers.initial.headscript.capture:

.. rubric:: Capturing Scripts Using the HeadScript Helper

Sometimes you need to generate client-side scripts programmatically. While you could use string concatenation,
heredocs, and the like, often it's easier just to do so by creating the script and sprinkling in *PHP* tags.
``HeadScript`` lets you do just that, capturing it to the stack:

.. code-block:: php
   :linenos:

   <?php $this->headScript()->captureStart() ?>
   var action = '<?php echo $this->baseUrl ?>';
   $('foo_form').action = action;
   <?php $this->headScript()->captureEnd() ?>

The following assumptions are made:

- The script will be appended to the stack. If you wish for it to replace the stack or be added to the top, you
  will need to pass 'SET' or 'PREPEND', respectively, as the first argument to ``captureStart()``.

- The script *MIME* type is assumed to be 'text/javascript'; if you wish to specify a different type, you will need
  to pass it as the second argument to ``captureStart()``.

- If you wish to specify any additional attributes for the **<script>** tag, pass them in an array as the third
  argument to ``captureStart()``.



.. _`Dojo`: http://www.dojotoolkit.org/