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form.js
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form.js
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/** section: DOM
* Form
*
* Utilities for dealing with forms in the DOM.
*
* [[Form]] is a namespace for all things form-related, packed with form
* manipulation and serialization goodness. While it holds methods dealing
* with forms as a whole, its submodule [[Form.Element]] deals with specific
* form controls.
*
* Many of these methods are also available directly on `form` elements.
**/
var Form = {
/**
* Form.reset(@form) -> Element
*
* Resets a form to its default values.
*
* Example usage:
*
* Form.reset('contact')
*
* // equivalent:
* $('contact').reset()
*
* // both have the same effect as pressing the reset button
*
* This method allows you to programatically reset a form. It is a wrapper
* for the `reset()` method native to `HTMLFormElement`.
**/
reset: function(form) {
form = $(form);
form.reset();
return form;
},
/**
* Form.serializeElements(elements[, options]) -> String | Object
* - elements (Array): A collection of elements to include in the
* serialization.
* - options (Object): _(Optional)_ A set of options that affect the return
* value of the method.
*
* Serialize an array of form elements to an object or string suitable
* for [[Ajax]] requests.
*
* As per the HTML spec, disabled fields are not included.
*
* If multiple elements have the same name and we're returning an object,
* the value for that key in the object will be an array of the field values
* in the order they appeared on the array of elements.
*
* The preferred method to serialize a form is [[Form.serialize]]. Refer to
* it for further information and examples on the `hash` option. However,
* with [[Form.serializeElements]] you can serialize *specific* input
* elements of your choice, allowing you to specify a subset of form elements
* that you want to serialize data from.
*
* ##### The Options
*
* The options allow you to control two things: What kind of return
* value you get (an object or a string), and whether and which `submit`
* fields are included in that object or string.
*
* If you do not supply an `options` object _at all_, the options
* `{ hash: false }` are used.
*
* If you supply an `options` object, it may have the following options:
*
* * `hash` ([[Boolean]]): `true` to return a plain object with keys and
* values (not a [[Hash]]; see below), `false` to return a String in query
* string format. If you supply an `options` object with no `hash` member,
* `hash` defaults to `true`. Note that this is __not__ the same as leaving
* off the `options` object entirely (see above).
*
* * `submit` ([[Boolean]] | [[String]]): In essence: If you omit this option
* the first submit button in the form is included; if you supply `false`,
* no submit buttons are included; if you supply the name of a submit
* button, the first button with that name is included. Note that the
* `false` value __must__ really be `false`, not _falsey_;
* falsey-but-not-false is like omitting the option.
*
* _(Deprecated)_ If you pass in a [[Boolean]] instead of an object for
* `options`, it is used as the `hash` option and all other options are
* defaulted.
*
* ##### A _hash_, not a [[Hash]]
*
* If you opt to receive an object, it is a plain JavaScript object with keys
* and values, __not__ a [[Hash]]. All JavaScript objects are hashes in the
* lower-case sense of the word, which is why the option has that
* somewhat-confusing name.
*
* ##### Examples
*
* To serialize all input elements of type "text":
*
* Form.serializeElements( $('myform').getInputs('text') )
* // -> serialized data
**/
serializeElements: function(elements, options) {
// An earlier version accepted a boolean second parameter (hash) where
// the default if omitted was false; respect that, but if they pass in an
// options object (e.g., the new signature) but don't specify the hash option,
// default true, as that's the new preferred approach.
if (typeof options != 'object') options = { hash: !!options };
else if (Object.isUndefined(options.hash)) options.hash = true;
var key, value, submitted = false, submit = options.submit, accumulator, initial;
if (options.hash) {
initial = {};
accumulator = function(result, key, value) {
if (key in result) {
if (!Object.isArray(result[key])) result[key] = [result[key]];
result[key] = result[key].concat(value);
} else result[key] = value;
return result;
};
} else {
initial = '';
accumulator = function(result, key, values) {
if (!Object.isArray(values)) {values = [values];}
if (!values.length) {return result;}
// According to the spec, spaces should be '+' rather than '%20'.
var encodedKey = encodeURIComponent(key).gsub(/%20/, '+');
return result + (result ? "&" : "") + values.map(function (value) {
// Normalize newlines as \r\n because the HTML spec says newlines should
// be encoded as CRLFs.
value = value.gsub(/(\r)?\n/, '\r\n');
value = encodeURIComponent(value);
// According to the spec, spaces should be '+' rather than '%20'.
value = value.gsub(/%20/, '+');
return encodedKey + "=" + value;
}).join("&");
};
}
return elements.inject(initial, function(result, element) {
if (!element.disabled && element.name) {
key = element.name; value = $(element).getValue();
if (value != null && element.type != 'file' && (element.type != 'submit' || (!submitted &&
submit !== false && (!submit || key == submit) && (submitted = true)))) {
result = accumulator(result, key, value);
}
}
return result;
});
}
};
Form.Methods = {
/**
* Form.serialize(@form[, options]) -> String | Object
* - options (Object): A list of options that affect the return value
* of the method.
*
* Serializes form data to a string suitable for [[Ajax]] requests (default
* behavior) or, if the `hash` option evaluates to `true`, an object hash
* where keys are form control names and values are data.
*
* Depending of whether or not the `hash` option evaluates to `true`, the
* result is either an object of the form `{name: "johnny", color: "blue"}`
* or a [[String]] of the form `"name=johnny&color=blue"`, suitable for
* parameters in an [[Ajax]] request. This method mimics the way browsers
* serialize forms natively so that form data can be sent without refreshing
* the page.
*
* See [[Form.serializeElements]] for more details on the options.
*
* ##### Examples
*
* $('person-example').serialize()
* // -> 'username=sulien&age=22&hobbies=coding&hobbies=hiking'
*
* $('person-example').serialize(true)
* // -> {username: 'sulien', age: '22', hobbies: ['coding', 'hiking']}
*
* ##### Notes
*
* Disabled form elements are not serialized (as per W3C HTML recommendation).
* Also, file inputs are skipped as they cannot be serialized and sent using
* only JavaScript.
**/
serialize: function(form, options) {
return Form.serializeElements(Form.getElements(form), options);
},
/**
* Form.getElements(@form) -> [Element...]
*
* Returns a collection of all controls within a form.
*
* ##### Note
*
* OPTION elements are not included in the result; only their parent
* SELECT control is.
**/
getElements: function(form) {
var elements = $(form).getElementsByTagName('*');
var element, results = [], serializers = Form.Element.Serializers;
for (var i = 0; element = elements[i]; i++) {
if (serializers[element.tagName.toLowerCase()])
results.push(Element.extend(element));
}
return results;
},
/**
* Form.getInputs(@form [, type [, name]]) -> [Element...]
* - type (String): A value for the `type` attribute against which to filter.
* - name (String): A value for the `name` attribute against which to filter.
*
* Returns a collection of all INPUT elements in a form.
*
* Use optional `type` and `name` arguments to restrict the search on
* these attributes.
*
* ##### Example
*
* var form = $('myform');
*
* form.getInputs(); // -> all INPUT elements
* form.getInputs('text'); // -> only text inputs
*
* var buttons = form.getInputs('radio', 'education');
* // -> only radio buttons of name "education"
*
* // now disable these radio buttons:
* buttons.invoke('disable');
*
* ##### Note
*
* Elements are returned in the *document* order, not the
* [tabindex order](http://www.w3.org/TR/html4/interact/forms.html#h-17.11.1).
**/
getInputs: function(form, typeName, name) {
form = $(form);
var inputs = form.getElementsByTagName('input');
if (!typeName && !name) return $A(inputs).map(Element.extend);
for (var i = 0, matchingInputs = [], length = inputs.length; i < length; i++) {
var input = inputs[i];
if ((typeName && input.type != typeName) || (name && input.name != name))
continue;
matchingInputs.push(Element.extend(input));
}
return matchingInputs;
},
/**
* Form.disable(@form) -> Element
*
* Disables the form as a whole. Form controls will be visible but
* uneditable.
*
* Disabling the form is done by iterating over form elements and calling
* [[Form.Element.disable]] on them.
*
* ##### Note
*
* Keep in mind that *disabled elements are skipped* by serialization
* methods! You cannot serialize a disabled form.
**/
disable: function(form) {
form = $(form);
Form.getElements(form).invoke('disable');
return form;
},
/**
* Form.enable(@form) -> Element
*
* Enables a fully- or partially-disabled form.
*
* Enabling the form is done by iterating over form elements and calling
* [[Form.Element.enable]] on them.
*
* ##### Note
*
* This will enable all form controls regardless of how they were disabled
* (by scripting or by HTML attributes).
**/
enable: function(form) {
form = $(form);
Form.getElements(form).invoke('enable');
return form;
},
/**
* Form.findFirstElement(@form) -> Element
*
* Finds the first non-hidden, non-disabled control within the form.
*
* The returned object is either an INPUT, SELECT or TEXTAREA element. This
* method is used by the [[Form.focusFirstElement]] method.
*
* ##### Note
*
* The result of this method is the element that comes first in the
* *document* order, not the
* [tabindex order](http://www.w3.org/TR/html4/interact/forms.html#h-17.11.1).
**/
findFirstElement: function(form) {
var elements = $(form).getElements().findAll(function(element) {
return 'hidden' != element.type && !element.disabled;
});
var firstByIndex = elements.findAll(function(element) {
return element.hasAttribute('tabIndex') && element.tabIndex >= 0;
}).sortBy(function(element) { return element.tabIndex }).first();
return firstByIndex ? firstByIndex : elements.find(function(element) {
return /^(?:input|select|textarea)$/i.test(element.tagName);
});
},
/**
* Form.focusFirstElement(@form) -> Element
*
* Gives keyboard focus to the first element of the form. Returns the form.
*
* Uses [[Form.findFirstElement]] to get the first element and calls
* [[Form.Element.activate]] on it. This is useful for enhancing usability on
* your site by bringing focus on page load to forms such as search forms or
* contact forms where a user is ready to start typing right away.
**/
focusFirstElement: function(form) {
form = $(form);
var element = form.findFirstElement();
if (element) element.activate();
return form;
},
/**
* Form.request(@form[, options]) -> Ajax.Request
* - options (Object): Options to pass along to the [[Ajax.Request]]
* constructor.
*
* A convenience method for serializing and submitting the form via an
* [[Ajax.Request]] to the URL of the form's `action` attribute.
*
* The `options` parameter is passed to the [[Ajax.Request]] instance,
* allowing one to override the HTTP method and/or specify additional
* parameters and callbacks.
*
* - If the form has a method attribute, its value is used for the
* [[Ajax.Request]] `method` option. If a method option is passed to
* `request()`, it takes precedence over the form's method attribute. If
* neither is specified, method defaults to "POST".
*
* - Key-value pairs specified in the `parameters` option (either as a hash
* or a query string) will be merged with (and *take precedence* over) the
* serialized form parameters.
*
* ##### Example
*
* Suppose you have this HTML form:
*
* language: html
* <form id="person-example" method="POST" action="/user/info">
* <fieldset><legend>User info</legend>
* <ul>
* <li>
* <label for="username">Username:</label>
* <input type="text" name="username" id="username" value="" />
* </li>
* <li>
* <label for="age">Age:</label>
* <input type="text" name="age" id="age" value="" size="3" />
* </li>
* <li>
* <label for="hobbies">Your hobbies are:</label>
* <select name="hobbies[]" id="hobbies" multiple="multiple">
* <option>coding</option>
* <option>swimming</option>
* <option>biking</option>
* <option>hiking</option>
* <option>drawing</option>
* </select>
* </li>
* </ul>
* <input type="submit" value="serialize!" />
* </fieldset>
* </form>
*
* You can easily post it with Ajax like this:
*
* $('person-example').request(); //done - it's posted
*
* // do the same with a callback:
* $('person-example').request({
* onComplete: function(){ alert('Form data saved!') }
* })
*
* To override the HTTP method and add some parameters, simply use `method`
* and `parameters` in the options. In this example we set the method to GET
* and set two fixed parameters:
* `interests` and `hobbies`. The latter already exists in the form but this
* value will take precedence.
*
* $('person-example').request({
* method: 'get',
* parameters: { interests:'JavaScript', 'hobbies[]':['programming', 'music'] },
* onComplete: function(){ alert('Form data saved!') }
* })
**/
request: function(form, options) {
form = $(form), options = Object.clone(options || { });
var params = options.parameters, action = form.readAttribute('action') || '';
if (action.blank()) action = window.location.href;
options.parameters = form.serialize(true);
if (params) {
if (Object.isString(params)) params = params.toQueryParams();
Object.extend(options.parameters, params);
}
if (form.hasAttribute('method') && !options.method)
options.method = form.method;
return new Ajax.Request(action, options);
}
};
/*--------------------------------------------------------------------------*/
/**
* Form.Element
*
* Utilities for dealing with form controls in the DOM.
*
* This is a collection of methods that assist in dealing with form controls.
* They provide ways to [[Form.Element.focus focus]], [[Form.Element.serialize
* serialize]], [[Form.Element.disable disable]]/[[Form.Element.enable enable]]
* or extract current value from a specific control.
*
* Note that nearly all these methods are available directly on `input`,
* `select`, and `textarea` elements. Therefore, these are equivalent:
*
* Form.Element.activate('myfield');
* $('myfield').activate();
*
* Naturally, you should always prefer the shortest form suitable in a
* situation. Most of these methods also return the element itself (as
* indicated by the return type) for chainability.
**/
Form.Element = {
/**
* Form.Element.focus(element) -> Element
*
* Gives keyboard focus to an element. Returns the element.
*
* ##### Example
*
* Form.Element.focus('searchbox')
*
* // Almost equivalent, but does NOT return the form element (uses the native focus() method):
* $('searchbox').focus()
**/
focus: function(element) {
$(element).focus();
return element;
},
/**
* Form.Element.select(element) -> Element
*
* Selects the current text in a text input. Returns the element.
*
* ##### Example
*
* Some search boxes are set up so that they auto-select their content when they receive focus.
*
* $('searchbox').onfocus = function() {
* Form.Element.select(this)
*
* // You can also rely on the native method, but this will NOT return the element!
* this.select()
* }
*
* ##### Focusing + selecting: use [[Form.Element.activate]]!
*
* The [[Form.Element.activate]] method is a nifty way to both focus a form
* field and select its current text, all in one portable JavaScript call.
**/
select: function(element) {
$(element).select();
return element;
}
};
Form.Element.Methods = {
/**
* Form.Element.serialize(@element) -> String
*
* Returns a URL-encoded string representation of a form control in the
* `name=value` format.
*
* The result of this method is a string suitable for Ajax requests. However,
* it serializes only a single element - if you need to serialize the whole
* form use [[Form.serialize]] instead.
*
* ##### Notes
*
* Serializing a disabled control or a one without a name will always result
* in an empty string.
*
* If you simply need an element's value for reasons other than Ajax
* requests, use [[Form.Element.getValue]] instead.
**/
serialize: function(element) {
element = $(element);
if (!element.disabled && element.name) {
var value = element.getValue();
if (value != undefined) {
var pair = { };
pair[element.name] = value;
return Object.toQueryString(pair);
}
}
return '';
},
/** alias of: $F
* Form.Element.getValue(@element) -> String | Array
*
* Returns the current value of a form control.
*
* A string is returned for most controls; only multiple `select` boxes
* return an array of values.
*
* The global shortcut for this method is [[$F]].
*
* ##### How to reference form controls by their _name_
*
* This method is consistent with other DOM extensions in that it requires an
* element **ID** as the string argument, not the name of the
* form control (as some might think). If you want to reference controls by
* their names, first find the control the regular JavaScript way and use the
* node itself instead of an ID as the argument.
*
* For example, if you have an `input` named "company" in a `form` with an
* ID "contact":
*
* var form = $('contact');
* var input = form['company'];
*
* Form.Element.getValue(input);
*
* // but, the preferred call is:
* $(input).getValue(); // we used the $() method so the node gets extended
*
* // you can also use the shortcut
* $F(input);
*
* ##### Note
*
* An error is thrown ("element has no properties") if the `element` argument
* is an unknown ID.
**/
getValue: function(element) {
element = $(element);
var method = element.tagName.toLowerCase();
return Form.Element.Serializers[method](element);
},
/**
* Form.Element.setValue(@element, value) -> Element
*
* Sets `value` to be the value of the form control. Returns the element.
**/
setValue: function(element, value) {
element = $(element);
var method = element.tagName.toLowerCase();
Form.Element.Serializers[method](element, value);
return element;
},
/**
* Form.Element.clear(@element) -> Element
*
* Clears the contents of a text input. Returns the element.
*
* ##### Example
*
* This code sets up a text field in a way that it clears its contents the
* first time it receives focus:
*
* $('some_field').onfocus = function() {
* // if already cleared, do nothing
* if (this._cleared) return
*
* // when this code is executed, "this" keyword will in fact be the field itself
* this.clear()
* this._cleared = true
* }
**/
clear: function(element) {
$(element).value = '';
return element;
},
/**
* Form.Element.present(@element) -> Element
*
* Returns `true` if a text input has contents, `false` otherwise.
*
* ##### Example
*
* This method is very handy in a generic form validation routine.
* On the following form's submit event, the presence of each text input is
* checked and lets the user know if they left a text input blank.
*
* language: html
* <form id="example" class="example" action="#">
* <fieldset>
* <legend>User Details</legend>
* <p id="msg" class="message">Please fill out the following fields:</p>
* <p>
* <label for="username">Username</label>
* <input id="username" type="text" name="username" />
* </p>
* <p>
* <label for="email">Email Address</label>
* <input id="email" type="text" name="email" />
* </p>
* <input type="submit" value="submit" />
* </fieldset>
* </form>
*
* <script type="text/javascript">
* $('example').onsubmit = function(){
* var valid, msg = $('msg')
*
* // are both fields present?
* valid = $(this.username).present() && $(this.email).present()
*
* if (valid) {
* // in the real world we would return true here to allow the form to be submitted
* // return true
* msg.update('Passed validation!').style.color = 'green'
* } else {
* msg.update('Please fill out <em>all</em> the fields.').style.color = 'red'
* }
* return false
* }
* </script>
**/
present: function(element) {
return $(element).value != '';
},
/**
* Form.Element.activate(@element) -> Element
*
* Gives focus to a form control and selects its contents if it is a text
* input.
*
* This method is just a shortcut for focusing and selecting; therefore,
* these are equivalent (aside from the fact that the former one will __not__
* return the field) :
*
* Form.Element.focus('myelement').select()
* $('myelement').activate()
*
* Guess which call is the nicest? ;)
**/
activate: function(element) {
element = $(element);
try {
element.focus();
if (element.select && (element.tagName.toLowerCase() != 'input' ||
!(/^(?:button|reset|submit)$/i.test(element.type))))
element.select();
} catch (e) { }
return element;
},
/**
* Form.Element.disable(@element) -> Element
*
* Disables a form control, effectively preventing its value from changing
* until it is enabled again.
*
* This method sets the native `disabled` property of an element to `true`.
* You can use this property to check the state of a control.
*
* ##### Notes
*
* Disabled form controls are never serialized.
*
* Never disable a form control as a security measure without having
* validation for it server-side. A user with minimal experience of
* JavaScript can enable these fields on your site easily using any browser.
* Instead, use disabling as a usability enhancement - with it you can
* indicate that a specific value should not be changed at the time being.
**/
disable: function(element) {
element = $(element);
element.disabled = true;
return element;
},
/**
* Form.Element.enable(@element) -> Element
*
* Enables a previously disabled form control.
**/
enable: function(element) {
element = $(element);
element.disabled = false;
return element;
}
};
/*--------------------------------------------------------------------------*/
var Field = Form.Element;
/** section: DOM, related to: Form
* $F(element) -> String | Array
*
* Returns the value of a form control. This is a convenience alias of
* [[Form.Element.getValue]]. Refer to it for full details.
**/
var $F = Form.Element.Methods.getValue;
/*--------------------------------------------------------------------------*/
Form.Element.Serializers = (function() {
function input(element, value) {
switch (element.type.toLowerCase()) {
case 'checkbox':
case 'radio':
return inputSelector(element, value);
default:
return valueSelector(element, value);
}
}
function inputSelector(element, value) {
if (Object.isUndefined(value))
return element.checked ? element.value : null;
else element.checked = !!value;
}
function valueSelector(element, value) {
if (Object.isUndefined(value)) return element.value;
else element.value = value;
}
function select(element, value) {
if (Object.isUndefined(value))
return (element.type === 'select-one' ? selectOne : selectMany)(element);
var opt, currentValue, single = !Object.isArray(value);
for (var i = 0, length = element.length; i < length; i++) {
opt = element.options[i];
currentValue = this.optionValue(opt);
if (single) {
if (currentValue == value) {
opt.selected = true;
return;
}
}
else opt.selected = value.include(currentValue);
}
}
function selectOne(element) {
var index = element.selectedIndex;
return index >= 0 ? optionValue(element.options[index]) : null;
}
function selectMany(element) {
var values, length = element.length;
if (!length) return null;
for (var i = 0, values = []; i < length; i++) {
var opt = element.options[i];
if (opt.selected) values.push(optionValue(opt));
}
return values;
}
function optionValue(opt) {
return Element.hasAttribute(opt, 'value') ? opt.value : opt.text;
}
return {
input: input,
inputSelector: inputSelector,
textarea: valueSelector,
select: select,
selectOne: selectOne,
selectMany: selectMany,
optionValue: optionValue,
button: valueSelector
};
})();
/*--------------------------------------------------------------------------*/
/** section: DOM
* Abstract
**/
/**
* class Abstract.TimedObserver
*
* An abstract DOM element observer class, subclasses of which can be used to
* periodically check a value and trigger a callback when the value has changed.
*
* A `TimedObserver` object will try to check a value using the `getValue()`
* instance method which must be defined by the subclass. There are two
* out-of-the-box subclasses:
* [[Form.Observer]], which serializes a form and triggers when the result has
* changed; and [[Form.Element.Observer]], which triggers when the value of a
* given form field changes.
*
*
* Using `TimedObserver` implementations is straightforward; simply instantiate
* them with appropriate arguments. For example:
*
* new Form.Element.Observer(
* 'myelement',
* 0.2, // 200 milliseconds
* function(el, value){
* alert('The form control has changed value to: ' + value)
* }
* )
*
* Now that we have instantiated an object, it will check the value of the form
* control every 0.2 seconds and alert us of any change. While it is useless to
* alert the user of his own input (like in the example), we could be doing
* something useful like updating a certain part of the UI or informing the
* application on server of stuff happening (over Ajax).
*
* The callback function is always called with 2 arguments: the element given
* when the observer instance was made and the actual value that has changed
* and caused the callback to be triggered in the first place.
*
* ##### Creating Your Own TimedObserver Implementations
*
* It's easy to create your own `TimedObserver` implementations: Simply subclass
* `TimedObserver` and provide the `getValue()` method. For example, this is the
* complete source code for [[Form.Element.Observer]]:
*
* Form.Element.Observer = Class.create(Abstract.TimedObserver, {
* getValue: function() {
* return Form.Element.getValue(this.element);
* }
* });
**/
Abstract.TimedObserver = Class.create(PeriodicalExecuter, {
/**
* new Abstract.TimedObserver(element, frequency, callback)
* - element (String | Element): The DOM element to watch. Can be an element
* instance or an ID.
* - frequency (Number): The frequency, in seconds — e.g., 0.33 to
* check for changes every third of a second.
* - callback (Function): The callback to trigger when the value changes.
*
* Initializes an [[Abstract.TimedObserver]]; used by subclasses.
**/
initialize: function($super, element, frequency, callback) {
$super(callback, frequency);
this.element = $(element);
this.lastValue = this.getValue();
},
execute: function() {
var value = this.getValue();
if (Object.isString(this.lastValue) && Object.isString(value) ?
this.lastValue != value : String(this.lastValue) != String(value)) {
this.callback(this.element, value);
this.lastValue = value;
}
}
});
/**
* class Form.Element.Observer < Abstract.TimedObserver
*
* An [[Abstract.TimedObserver]] subclass that watches for changes to a form
* field's value. This triggers the callback when the form field's value
* (according to [[Form.Element.getValue]]) changes. (Note that when the value
* actually changes can vary from browser to browser, particularly with
* `select` boxes.)
*
* Form.Element observer implements the `getValue()` method using
* [[Form.Element.getValue]] on the given element. See [[Abstract.TimedObserver]]
* for general documentation on timed observers.
**/
Form.Element.Observer = Class.create(Abstract.TimedObserver, {
/**
* new Form.Element.Observer(element, frequency, callback)
* - element (String | Element): The form element to watch. Can be an element instance or an ID.
* - frequency (Number): The frequency, in seconds — e.g., 0.33 to check for changes every
* third of a second.
* - callback (Function): The callback to trigger when the value changes.
*
* Creates a [[Form.Element.Observer]].
**/
getValue: function() {
return Form.Element.getValue(this.element);
}
});
/**
* class Form.Observer < Abstract.TimedObserver
*
* An [[Abstract.TimedObserver]] subclass that watches for changes to a form.
* The callback is triggered when the form changes — e.g., when any
* of its fields' values changes, when fields are added/removed, etc.; anything
* that affects the serialized form of the form (see [[Form#serialize]]).
*
* ##### Example
*
* In this example an `observer` is used to change the appearance of the form
* if any of the values had been changed. It returns to its initial state when
* the data is submitted (saved).
*
* language: html
* <form id="example" action="#">
* <fieldset>
* <legend>Login Preferences</legend>
* <p id="msg" class="message">Current settings:</p>
* <p>
* <label for="greeting">Greeting message</label>
* <input id="greeting" type="text" name="greeting" value="Hello world!" />
* </p>
* <h4>Login options</h4>
* <p>
* <input id="login-visible" type="checkbox" name="login-visible" checked="checked" />
* <label for="login-visible">allow others to see my last login date</label>
* </p>
* <p>
* <input id="land-recent" type="checkbox" name="land-recent" />
* <label for="land-recent">land on recent changes overview instead of the Dashboard</label>
* </p>
* <input type="submit" value="save" />
* </fieldset>
* </form>
*
* <script type="text/javascript">
* new Form.Observer('example', 0.3, function(form, value){
* $('msg').update('Your preferences have changed. Resubmit to save').style.color = 'red'
* form.down().setStyle({ background:'lemonchiffon', borderColor:'red' })
* })
*
* $('example').onsubmit = function() {
* $('msg').update('Preferences saved!').style.color = 'green'
* this.down().setStyle({ background:null, borderColor:null })
* return false
* }
* </script>
**/
Form.Observer = Class.create(Abstract.TimedObserver, {
/**
* new Form.Observer(element, frequency, callback)
* - element (String | Element): The element of the form to watch. Can be an element
* instance or an ID.
* - frequency (Number): The frequency, in seconds -- e.g., 0.33 to check for changes every
* third of a second.
* - callback (Function): The callback to trigger when the form changes.
*
* Creates a [[Form.Observer]].
**/
getValue: function() {
return Form.serialize(this.element);
}
});
/*--------------------------------------------------------------------------*/
/**
* class Abstract.EventObserver
**/
Abstract.EventObserver = Class.create({
initialize: function(element, callback) {
this.element = $(element);
this.callback = callback;
this.lastValue = this.getValue();
if (this.element.tagName.toLowerCase() == 'form')
this.registerFormCallbacks();
else
this.registerCallback(this.element);
},
onElementEvent: function() {
var value = this.getValue();