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/* vim:set ts=2 sw=2 sts=2 et: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
// Utility function that returns copy of the given `text` with last character
// removed if it is `"s"`.
function singularify(text) {
return text[text.length - 1] === "s" ? text.substr(0, text.length - 1) : text;
}
// Utility function that takes event type, argument is passed to
// `document.createEvent` and returns name of the initializer method of the
// given event. Please note that there are some event types whose initializer
// methods can't be guessed by this function. For more details see following
// link: https://developer.mozilla.org/En/DOM/Document.createEvent
function getInitializerName(category) {
return "init" + singularify(category);
}
/**
* Registers an event `listener` on a given `element`, that will be called
* when events of specified `type` is dispatched on the `element`.
* @param {Element} element
* Dom element to register listener on.
* @param {String} type
* A string representing the
* [event type](https://developer.mozilla.org/en/DOM/event.type) to
* listen for.
* @param {Function} listener
* Function that is called whenever an event of the specified `type`
* occurs.
* @param {Boolean} capture
* If true, indicates that the user wishes to initiate capture. After
* initiating capture, all events of the specified type will be dispatched
* to the registered listener before being dispatched to any `EventTarget`s
* beneath it in the DOM tree. Events which are bubbling upward through
* the tree will not trigger a listener designated to use capture.
* See [DOM Level 3 Events](http://www.w3.org/TR/DOM-Level-3-Events/#event-flow)
* for a detailed explanation.
*/
function on(element, type, listener, capture) {
// `capture` defaults to `false`.
capture = capture || false;
element.addEventListener(type, listener, capture);
}
exports.on = on;
/**
* Registers an event `listener` on a given `element`, that will be called
* only once, next time event of specified `type` is dispatched on the
* `element`.
* @param {Element} element
* Dom element to register listener on.
* @param {String} type
* A string representing the
* [event type](https://developer.mozilla.org/en/DOM/event.type) to
* listen for.
* @param {Function} listener
* Function that is called whenever an event of the specified `type`
* occurs.
* @param {Boolean} capture
* If true, indicates that the user wishes to initiate capture. After
* initiating capture, all events of the specified type will be dispatched
* to the registered listener before being dispatched to any `EventTarget`s
* beneath it in the DOM tree. Events which are bubbling upward through
* the tree will not trigger a listener designated to use capture.
* See [DOM Level 3 Events](http://www.w3.org/TR/DOM-Level-3-Events/#event-flow)
* for a detailed explanation.
*/
function once(element, type, listener, capture) {
on(element, type, function selfRemovableListener(event) {
removeListener(element, type, selfRemovableListener, capture);
listener.apply(this, arguments);
}, capture);
}
exports.once = once;
/**
* Unregisters an event `listener` on a given `element` for the events of the
* specified `type`.
*
* @param {Element} element
* Dom element to unregister listener from.
* @param {String} type
* A string representing the
* [event type](https://developer.mozilla.org/en/DOM/event.type) to
* listen for.
* @param {Function} listener
* Function that is called whenever an event of the specified `type`
* occurs.
* @param {Boolean} capture
* If true, indicates that the user wishes to initiate capture. After
* initiating capture, all events of the specified type will be dispatched
* to the registered listener before being dispatched to any `EventTarget`s
* beneath it in the DOM tree. Events which are bubbling upward through
* the tree will not trigger a listener designated to use capture.
* See [DOM Level 3 Events](http://www.w3.org/TR/DOM-Level-3-Events/#event-flow)
* for a detailed explanation.
*/
function removeListener(element, type, listener, capture) {
element.removeEventListener(type, listener, capture);
}
exports.removeListener = removeListener;
/**
* Emits event of the specified `type` and `category` on the given `element`.
* Specified `settings` are used to initialize event before dispatching it.
* @param {Element} element
* Dom element to dispatch event on.
* @param {String} type
* A string representing the
* [event type](https://developer.mozilla.org/en/DOM/event.type).
* @param {Object} options
* Options object containing following properties:
* - `category`: String passed to the `document.createEvent`. Option is
* optional and defaults to "UIEvents".
* - `initializer`: If passed it will be used as name of the method used
* to initialize event. If omitted name will be generated from the
* `category` field by prefixing it with `"init"` and removing last
* character if it matches `"s"`.
* - `settings`: Array of settings that are forwarded to the event
* initializer after firs `type` argument.
* @see https://developer.mozilla.org/En/DOM/Document.createEvent
*/
function emit(element, type, { category, initializer, settings }) {
category = category || "UIEvents";
initializer = initializer || getInitializerName(category);
let document = element.ownerDocument;
let event = document.createEvent(category);
event[initializer].apply(event, [type].concat(settings));
element.dispatchEvent(event);
};
exports.emit = emit;
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