@enact/core/dispatcher/dispatcher.js

Enact is an open source JavaScript framework containing everything you need to create a fast, scalable mobile or web application.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.setDefaultTargetById = exports.once = exports.on = exports.off = void 0;
var _curry = _interopRequireDefault(require("ramda/src/curry"));
var _listeners = require("./listeners");
function _interopRequireDefault(e) { return e && e.__esModule ? e : { "default": e }; }
/**
 * Provides methods to add and remove global event listeners.
 *
 * @module core/dispatcher
 * @exports off
 * @exports on
 * @exports once
 */

var defaultTarget = typeof document === 'object' && document;
var rootId;

/*
 * Sets a selector for the default target. If no selector is set, `document` is the default target.
 *
 * @function
 * @param	{String}	id	Node id of the default target
 *
 * @returns {undefined}
 * @memberof core/dispatcher
 * @private
 */
var setDefaultTargetById = exports.setDefaultTargetById = function setDefaultTargetById(id) {
  defaultTarget = typeof document === 'object' && document.querySelector('#' + id) || defaultTarget;
  rootId = id;
};

/*
 * Checks if the default target of `document` exists before returning it, otherwise returns `false`.
 * If the default target is falsy and the stored id of the root exists, it tries to find the
 * default target based on the id.
 *
 * @function
 *
 * @returns {Node|Boolean}
 * @memberof core/dispatcher
 * @private
 */
var getDefaultTarget = function getDefaultTarget() {
  if (!defaultTarget && rootId) {
    setDefaultTargetById(rootId);
  }
  return defaultTarget;
};

/*
 * Wraps event callbacks with a try-catch block to prevent unrelated code from blocking.
 *
 * @function
 * @param	{Event}		ev	Event payload
 * @param	{Function}	fn	Event callback
 *
 * @returns	{undefined}
 * @memberof core/dispatcher
 * @private
 */
var invoker = (0, _curry["default"])(function (ev, fn) {
  try {
    fn(ev);
  } catch (e) {
    // eslint-disable-next-line no-console
    console.error("A ".concat(e.name, " occurred during event handling with the message '").concat(e.message, "'"));
  }
});

/*
 * Dispatches an event to the registered handlers.
 *
 * @function
 * @param	{Event}		ev	Event payload
 *
 * @returns {undefined}
 * @memberof core/dispatcher
 * @private
 */
var dispatcher = function dispatcher(ev) {
  var name = ev.type;
  var listeners = (0, _listeners.getListeners)(ev.currentTarget, name);
  if (listeners) {
    var inv = invoker(ev);
    listeners.forEach(inv);
  }
};

/**
 * Adds a new global event listener. Duplicate event handlers will be discarded.
 *
 * @function
 * @param	{String}	name				Event name
 * @param	{Function}	fn					Event handler
 * @param	{Node}		[target='document']	Event listener target
 *
 * @returns {undefined}
 * @memberof core/dispatcher
 * @public
 */
var on = exports.on = function on(name, fn) {
  var target = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : getDefaultTarget();
  if (target) {
    var added = (0, _listeners.addListener)(target, name, fn);
    if (added && (0, _listeners.getListeners)(target, name).length === 1) {
      target.addEventListener(name, dispatcher);
    }
  }
};

/**
 * Removes a global event listener.
 *
 * @function
 * @param	{String}	name				Event name
 * @param	{Function}	fn					Event handler
 * @param	{Node}		[target=`document`]	Event listener target
 *
 * @returns {undefined}
 * @memberof core/dispatcher
 * @public
 */
var off = exports.off = function off(name, fn) {
  var target = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : getDefaultTarget();
  if (target) {
    var listeners = (0, _listeners.getListeners)(target, name);
    var index = listeners.indexOf(fn);
    if (index >= 0) {
      listeners.splice(index, 1);
      if (listeners.length === 0) {
        target.removeEventListener(name, dispatcher);
      }
    }
  }
};

/**
 * Adds a new global event listener that removes itself after handling one event.
 *
 * @function
 * @param	{String}	name		Event name
 * @param	{Function}	fn			Event handler
 * @param	{Node}		[target]	Event listener target
 *
 * @returns {Function}				The single-use handler. To remove the handler manually, call
 *									the `off()` function with this as the 2nd parameter.
 * @memberof core/dispatcher
 * @public
 */
var once = exports.once = function once(name, fn, target) {
  var _onceFn = function onceFn(ev) {
    fn(ev);
    off(name, _onceFn, target);
  };
  on(name, _onceFn, target);
  return _onceFn;
};