interactjs/src/utils/events.js

Drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE9+)

const is           = require('./is');
const domUtils     = require('./domUtils');
const pointerUtils = require('./pointerUtils');
const pExtend      = require('./pointerExtend');

const { window }   = require('./window');
const { contains } = require('./arr');

const elements = [];
const targets  = [];

// {
//   type: {
//     selectors: ['selector', ...],
//     contexts : [document, ...],
//     listeners: [[listener, capture, passive], ...]
//   }
//  }
const delegatedEvents = {};
const documents       = [];

const supportsOptions = (() => {
  let supported = false;

  window.document.createElement('div').addEventListener('test', null, {
    get capture () { supported = true; },
  });

  return supported;
})();

function add (element, type, listener, optionalArg) {
  const options = getOptions(optionalArg);
  let elementIndex = elements.indexOf(element);
  let target = targets[elementIndex];

  if (!target) {
    target = {
      events: {},
      typeCount: 0,
    };

    elementIndex = elements.push(element) - 1;
    targets.push(target);
  }

  if (!target.events[type]) {
    target.events[type] = [];
    target.typeCount++;
  }

  if (!contains(target.events[type], listener)) {
    element.addEventListener(type, listener, supportsOptions? options : !!options.capture);
    target.events[type].push(listener);
  }
}

function remove (element, type, listener, optionalArg) {
  const options = getOptions(optionalArg);
  const elementIndex = elements.indexOf(element);
  const target = targets[elementIndex];

  if (!target || !target.events) {
    return;
  }

  if (type === 'all') {
    for (type in target.events) {
      if (target.events.hasOwnProperty(type)) {
        remove(element, type, 'all');
      }
    }
    return;
  }

  if (target.events[type]) {
    const len = target.events[type].length;

    if (listener === 'all') {
      for (let i = 0; i < len; i++) {
        remove(element, type, target.events[type][i], options);
      }
      return;
    }
    else {
      for (let i = 0; i < len; i++) {
        if (target.events[type][i] === listener) {
          element.removeEventListener(`on${type}`, listener, supportsOptions? options : !!options.capture);
          target.events[type].splice(i, 1);

          break;
        }
      }
    }

    if (target.events[type] && target.events[type].length === 0) {
      target.events[type] = null;
      target.typeCount--;
    }
  }

  if (!target.typeCount) {
    targets.splice(elementIndex, 1);
    elements.splice(elementIndex, 1);
  }
}

function addDelegate (selector, context, type, listener, optionalArg) {
  const options = getOptions(optionalArg);
  if (!delegatedEvents[type]) {
    delegatedEvents[type] = {
      selectors: [],
      contexts : [],
      listeners: [],
    };

    // add delegate listener functions
    for (const doc of documents) {
      add(doc, type, delegateListener);
      add(doc, type, delegateUseCapture, true);
    }
  }

  const delegated = delegatedEvents[type];
  let index;

  for (index = delegated.selectors.length - 1; index >= 0; index--) {
    if (delegated.selectors[index] === selector
        && delegated.contexts[index] === context) {
      break;
    }
  }

  if (index === -1) {
    index = delegated.selectors.length;

    delegated.selectors.push(selector);
    delegated.contexts .push(context);
    delegated.listeners.push([]);
  }

  // keep listener and capture and passive flags
  delegated.listeners[index].push([listener, !!options.capture, options.passive]);
}

function removeDelegate (selector, context, type, listener, optionalArg) {
  const options = getOptions(optionalArg);
  const delegated = delegatedEvents[type];
  let matchFound = false;
  let index;

  if (!delegated) { return; }

  // count from last index of delegated to 0
  for (index = delegated.selectors.length - 1; index >= 0; index--) {
    // look for matching selector and context Node
    if (delegated.selectors[index] === selector
        && delegated.contexts[index] === context) {

      const listeners = delegated.listeners[index];

      // each item of the listeners array is an array: [function, capture, passive]
      for (let i = listeners.length - 1; i >= 0; i--) {
        const [fn, capture, passive] = listeners[i];

        // check if the listener functions and capture and passive flags match
        if (fn === listener && capture === !!options.capture && passive === options.passive) {
          // remove the listener from the array of listeners
          listeners.splice(i, 1);

          // if all listeners for this interactable have been removed
          // remove the interactable from the delegated arrays
          if (!listeners.length) {
            delegated.selectors.splice(index, 1);
            delegated.contexts .splice(index, 1);
            delegated.listeners.splice(index, 1);

            // remove delegate function from context
            remove(context, type, delegateListener);
            remove(context, type, delegateUseCapture, true);

            // remove the arrays if they are empty
            if (!delegated.selectors.length) {
              delegatedEvents[type] = null;
            }
          }

          // only remove one listener
          matchFound = true;
          break;
        }
      }

      if (matchFound) { break; }
    }
  }
}

// bound to the interactable context when a DOM event
// listener is added to a selector interactable
function delegateListener (event, optionalArg) {
  const options = getOptions(optionalArg);
  const fakeEvent = {};
  const delegated = delegatedEvents[event.type];
  const [eventTarget] = (pointerUtils.getEventTargets(event));
  let element = eventTarget;

  // duplicate the event so that currentTarget can be changed
  pExtend(fakeEvent, event);

  fakeEvent.originalEvent = event;
  fakeEvent.preventDefault = preventOriginalDefault;

  // climb up document tree looking for selector matches
  while (is.element(element)) {
    for (let i = 0; i < delegated.selectors.length; i++) {
      const selector = delegated.selectors[i];
      const context = delegated.contexts[i];

      if (domUtils.matchesSelector(element, selector)
          && domUtils.nodeContains(context, eventTarget)
          && domUtils.nodeContains(context, element)) {

        const listeners = delegated.listeners[i];

        fakeEvent.currentTarget = element;

        for (let j = 0; j < listeners.length; j++) {
          const [fn, capture, passive] = listeners[j];

          if (capture === !!options.capture && passive === options.passive) {
            fn(fakeEvent);
          }
        }
      }
    }

    element = domUtils.parentNode(element);
  }
}

function delegateUseCapture (event) {
  return delegateListener.call(this, event, true);
}

function preventOriginalDefault () {
  this.originalEvent.preventDefault();
}

function getOptions (param) {
  return is.object(param)? param : { capture: param };
}

module.exports = {
  add,
  remove,

  addDelegate,
  removeDelegate,

  delegateListener,
  delegateUseCapture,
  delegatedEvents,
  documents,

  supportsOptions,

  _elements: elements,
  _targets: targets,
};