tui-code-snippet/domEvent/on.js

TOAST UI Utility: CodeSnippet

/**
 * @fileoverview Bind DOM events
 * @author NHN FE Development Lab <dl_javascript@nhn.com>
 */

'use strict';

var isString = require('../type/isString');
var forEach = require('../collection/forEach');

var safeEvent = require('./_safeEvent');

/**
 * Bind DOM events.
 * @param {HTMLElement} element - element to bind events
 * @param {(string|object)} types - Space splitted events names or eventName:handler object
 * @param {(function|object)} handler - handler function or context for handler method
 * @param {object} [context] context - context for handler method.
 * @memberof module:domEvent
 * @example
 * const div = document.querySelector('div');
 * 
 * // Bind one event to an element.
 * on(div, 'click', toggle);
 * 
 * // Bind multiple events with a same handler to multiple elements at once.
 * // Use event names splitted by a space.
 * on(div, 'mouseenter mouseleave', changeColor);
 * 
 * // Bind multiple events with different handlers to an element at once.
 * // Use an object which of key is an event name and value is a handler function.
 * on(div, {
 *   keydown: highlight,
 *   keyup: dehighlight
 * });
 * 
 * // Set a context for handler method.
 * const name = 'global';
 * const repository = {name: 'CodeSnippet'};
 * on(div, 'drag', function() {
 *   console.log(this.name);
 * }, repository);
 * // Result when you drag a div: "CodeSnippet"
 */
function on(element, types, handler, context) {
  if (isString(types)) {
    forEach(types.split(/\s+/g), function(type) {
      bindEvent(element, type, handler, context);
    });

    return;
  }

  forEach(types, function(func, type) {
    bindEvent(element, type, func, handler);
  });
}

/**
 * Bind DOM events
 * @param {HTMLElement} element - element to bind events
 * @param {string} type - events name
 * @param {function} handler - handler function or context for handler method
 * @param {object} [context] context - context for handler method.
 * @private
 */
function bindEvent(element, type, handler, context) {
  /**
     * Event handler
     * @param {Event} e - event object
     */
  function eventHandler(e) {
    handler.call(context || element, e || window.event);
  }

  if ('addEventListener' in element) {
    element.addEventListener(type, eventHandler);
  } else if ('attachEvent' in element) {
    element.attachEvent('on' + type, eventHandler);
  }
  memorizeHandler(element, type, handler, eventHandler);
}

/**
 * Memorize DOM event handler for unbinding.
 * @param {HTMLElement} element - element to bind events
 * @param {string} type - events name
 * @param {function} handler - handler function that user passed at on() use
 * @param {function} wrappedHandler - handler function that wrapped by domevent for implementing some features
 * @private
 */
function memorizeHandler(element, type, handler, wrappedHandler) {
  var events = safeEvent(element, type);
  var existInEvents = false;

  forEach(events, function(obj) {
    if (obj.handler === handler) {
      existInEvents = true;

      return false;
    }

    return true;
  });

  if (!existInEvents) {
    events.push({
      handler: handler,
      wrappedHandler: wrappedHandler
    });
  }
}

module.exports = on;