JavaScript

As of Elgg 1.9, we encourage all developers to adopt the AMD (Asynchronous Module Definition) standard for writing JavaScript code in Elgg. The 1.8 version is still functional and is described below.

AMD

Here we’ll describe making and executing AMD modules. The RequireJS documentation for defining modules may also be of use.

Executing a module in the current page

Telling Elgg to load an existing module in the current page is easy:

<?php
elgg_require_js("myplugin/say_hello");

On the client-side, this will asynchronously load the module, load any dependencies, and execute the module’s definition function, if it has one.

Defining the Module

Here we define a basic module that alters the page, by passing a “definition function” to define():

// in views/default/js/myplugin/say_hello.js

define(function(require) {
    var elgg = require("elgg");
    var $ = require("jquery");

    $('body').append(elgg.echo('hello_world'));
});

The module’s name is determined by the view name, which here is js/myplugin/say_hello.js. We strip the leading js/ and the .js extension, leaving myplugin/say_hello.

Warning

The definition function must have one argument named require.

Making modules dependent on other modules

Below we refactor a bit so that the module depends on a new myplugin/hello module to provide the greeting:

// in views/default/js/myplugin/hello.js

define(function(require) {
    var elgg = require("elgg");

    return elgg.echo('hello_world');
});
// in views/default/js/myplugin/say_hello.js

define(function(require) {
    var $ = require("jquery");
    var hello = require("myplugin/hello");

    $('body').append(hello);
});

Passing plugin/Elgg settings to modules

You can use a PHP-based module to pass values from the server. To make the module myplugin/settings, create the view file views/default/js/myplugin/settings.js.php (note the double extension .js.php).

<?php

$settings = elgg_get_plugin_from_id('myplugin')->getAllSettings();
$settings = [
    'foo' => elgg_extract('foo', $settings),
    'bar' => elgg_extract('bar', $settings),
];

?>
define(<?php echo json_encode($settings); ?>);

You must also manually register the view as an external resource:

<?php
// note the view name does not include ".php"
elgg_register_simplecache_view('js/myplugin/settings.js');

Note

The PHP view is cached, so you should treat the output as static (the same for all users) and avoid session-specific logic.

Setting the URL of a module

You may have a script outside your views you wish to make available as a module.

In your PHP init, system event handler, you can use elgg_define_js() to do this:

<?php
elgg_define_js('underscore', [
    'src' => '/mod/myplugin/vendors/underscore/underscore-min.js',
]);

Note

The src option in elgg_define_js() is passed through elgg_normalize_url, so you can use paths relative to the site URL.

Using traditional JS libraries as modules

JavaScript libraries that define global resources can also be defined as AMD modules if you shim them by setting exports and optionally deps:

<?php
// set the path, define its dependencies, and what value it returns
elgg_define_js('jquery.form', [
    'src' => '/mod/myplugin/vendors/jquery.form.js',
    'deps' => array('jquery'),
    'exports' => 'jQuery.fn.ajaxForm',
]);

When this is requested client-side:

  1. The jQuery module is loaded, as it’s marked as a dependency.
  2. http://example.org/elgg/mod/myplugin/vendors/jquery/jquery.form.js is loaded and executed.
  3. The value of window.jQuery.fn.ajaxForm is returned by the module.

Warning

Calls to elgg_define_js() must be in an init, system event handler.

Some things to note

  1. Do not use elgg.provide() anymore nor other means to attach code to elgg or other global objects. Use modules.
  2. Return the value of the module instead of adding to a global variable.
  3. JS and CSS views (names starting with js/ or css/) as well as static (.js/.css) files are automatically minified and cached by Elgg’s simplecache system.

Migrating JS from Elgg 1.8 to AMD / 1.9

Current 1.8 JavaScript modules will continue to work with Elgg.

We do not anticipate any backwards compatibility issues with this new direction and will fix any issues that do come up. The old system will still be functional in Elgg 1.9, but developers are encouraged to begin looking to AMD as the future of JS in Elgg.

Traditional JavaScript (1.8)

Register third-party libraries with elgg_register_js:

elgg_register_js('jquery', $cdnjs_url);

This will override any URLs previously registered under this name.

Load a library on the current page with elgg_load_js:

elgg_load_js('jquery');

This will include and execute the linked code.

Tip

Using inline scripts is strongly discouraged because:
  • They are not testable (maintainability)
  • They are not cacheable (performance)
  • Doing so forces some scripts to be loaded in <head> (performance)

Inline scripts in core or bundled plugins are considered legacy bugs.

Core functions available in JS

elgg.echo()

Translate interface text

elgg.echo('example:text', ['arg1']);

elgg.system_message()

Display a status message to the user.

elgg.system_message(elgg.echo('success'));

elgg.register_error()

Display an error message to the user.

elgg.register_error(elgg.echo('error'));

elgg.forward()

elgg.normalize_url()

Normalize a URL relative to the elgg root:

// "http://localhost/elgg/blog"
elgg.normalize_url('/blog');

Redirect to a new page.

elgg.forward('/blog');

This function automatically normalizes the URL.

elgg.parse_url()

Parse a URL into its component parts:

// returns {
//   fragment: "fragment",
//   host: "community.elgg.org",
//   path: "/file.php",
//   query: "arg=val"
// }
elgg.parse_url(
  'http://community.elgg.org/file.php?arg=val#fragment');

elgg.get_page_owner_guid()

Get the GUID of the current page’s owner.

elgg.register_hook_handler()

Register a hook handler with the event system.

// old initialization style
elgg.register_hook_handler('init', 'system', my_plugin.init);

// new: AMD module
define(function (require) {
    var elgg = require('elgg');

    // [init, system] has fired
});

elgg.trigger_hook()

Emit a hook event in the event system.

// allow other plugins to alter value
value = elgg.trigger_hook('my_plugin:filter', 'value', {}, value);

elgg.security.refreshToken()

Force a refresh of all XSRF tokens on the page.

This is automatically called every 5 minutes by default.

This requires a valid security token in 1.8, but not in 1.9.

The user will be warned if their session has expired.

elgg.security.addToken()

Add a security token to an object, URL, or query string:

// returns {
//   __elgg_token: "1468dc44c5b437f34423e2d55acfdd87",
//   __elgg_ts: 1328143779,
//   other: "data"
// }
elgg.security.addToken({'other': 'data'});

// returns: "action/add?__elgg_ts=1328144079&__elgg_token=55fd9c2d7f5075d11e722358afd5fde2"
elgg.security.addToken("action/add");

// returns "?arg=val&__elgg_ts=1328144079&__elgg_token=55fd9c2d7f5075d11e722358afd5fde2"
elgg.security.addToken("?arg=val");

elgg.get_logged_in_user_entity()

Returns the logged in user as an JS ElggUser object.

elgg.get_logged_in_user_guid()

Returns the logged in user’s guid.

elgg.is_logged_in()

True if the user is logged in.

elgg.is_admin_logged_in()

True if the user is logged in and is an admin.

elgg.config.get_language()

Get the current page’s language.

There are a number of configuration values set in the elgg object:

// The root of the website.
elgg.config.wwwroot;
// The default site language.
elgg.config.language;
// The current page's viewtype
elgg.config.viewtype;
// The Elgg version (YYYYMMDDXX).
elgg.config.version;
// The Elgg release (X.Y.Z).
elgg.config.release;

Module elgg/spinner

The elgg/spinner module can be used to create an Ajax loading indicator fixed to the top of the window.

define(function (require) {
   var spinner = require('elgg/spinner');

   elgg.action('friend/add', {
       beforeSend: spinner.start,
       complete: spinner.stop,
       success: function (json) {
           // ...
       }
   });
});

Hooks

The JS engine has a hooks system similar to the PHP engine’s plugin hooks: hooks are triggered and plugins can register callbacks to react or alter information. There is no concept of Elgg events in the JS engine; everything in the JS engine is implemented as a hook.

Registering a callback to a hook

Callbacks are registered using elgg.register_hook_handler(). Multiple callbacks can be registered for the same hook.

The following example registers the elgg.ui.initDatePicker callback for the init, system event. Note that a difference in the JS engine is that instead of passing a string you pass the function itself to elgg.register_hook_handler() as the callback.

elgg.provide('elgg.ui.initDatePicker');
elgg.ui.initDatePicker = function() { ... }

elgg.register_hook_handler('init', 'system', elgg.ui.initDatePicker);

The callback

The callback accepts 4 arguments:

  • hook - The hook name
  • type - The hook type
  • params - An object or set of parameters specific to the hook
  • value - The current value

The value will be passed through each hook. Depending on the hook, callbacks can simply react or alter data.

Triggering custom hooks

Plugins can trigger their own hooks:

elgg.hook.trigger_hook('name', 'type', {params}, "value");

Available hooks

init, system
This hook is fired when the JS system is ready. Plugins should register their init functions for this hook.
ready, system
This hook is fired when the system has fully booted.
getOptions, ui.popup
This hook is fired for pop up displays (“rel”=”popup”) and allows for customized placement options.