HeadScript

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:

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.

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.

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

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.

// jquery template
$template = '<div class="book"{{:title}}</div';

$this->headScript()->appendScript(
    $template,
    'text/x-jquery-tmpl',
    ['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 = null, $placement = 'APPEND', array $attrs = [], $type = 'text/javascript'). 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'. $attrs is an array of script attributes. $type is the script type attribute.

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 modifying the object returned.

The HeadScript helper is a concrete implementation of the Placeholder helper.

Use InlineScript for HTML Body Scripts

HeadScript's sibling helper, 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.

Arbitrary Attributes are Disabled by Default

By default, HeadScript only will render <script> attributes that are blessed by the W3C. These include id, charset, crossorigin, defer, integrity, language, src, and type. 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:

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

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.

// 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:

// 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:

<?= $this->headScript() ?>

Capturing Scripts

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:

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

The following assumptions are made: