vant/packages/swipe/utils.js

import Vue from 'vue';

var extend = Object.assign.bind(Object);

function EventEmitter() {
  this.__events = {};
}
EventEmitter.prototype = {
  on: function(name, cb) {
    this.__events[name] || (this.__events[name] = []);
    this.__events[name].push(cb);
    return this;
  },
  emit: function(name) {
    var arr = this.__events[name];
    var argus = Array.prototype.slice.call(arguments, 1);
    var self = this;
    if (arr) {
      arr.forEach(function(cb) {
        cb.apply(self, argus);
      });
    }
  },
  removeListener: function(name, fn) {
    if (!this.__events[name]) {
      return;
    }
    let index;
    if (fn) {
      index = this.__events[name].indexOf(fn);
      if (index > 0) {
        this.__events[name].splice(index, 1);
      }
    } else {
      delete this.__events[name];
    }
  }
};

const isSupportRequestAnimationFrame = !Vue.prototype.$isServer &&
  (window.requestAnimationFrame ||
  window.mozRequestAnimationFrame ||
  window.webkitRequestAnimationFrame ||
  window.msRequestAnimationFrame);
const isSupportCancelAnimationFrame = !Vue.prototype.$isServer &&
  (window.cancelAnimationFrame ||
  window.mozCancelAnimationFrame ||
  window.webkitCancelAnimationFrame ||
  window.msCancelAnimationFrame);

const requestAnimationFrame = isSupportRequestAnimationFrame || function(callback, element) {
  return window.setTimeout(callback, 1000 / 60);
};

const cancelAnimationFrame = isSupportCancelAnimationFrame || function(id) {
  clearTimeout(id);
};

const bindEvents = (elem, eventNames, fn) => {
  eventNames = eventNames.split(/\s+/);
  eventNames.forEach(eventName => elem.addEventListener(eventName, fn));
};

const removeEvents = (elem, eventNames, fn) => {
  eventNames = eventNames.split(/\s+/);
  eventNames.forEach(eventName => elem.removeEventListener(eventName, fn));
};

export {
  extend,
  EventEmitter,
  requestAnimationFrame,
  cancelAnimationFrame,
  bindEvents,
  removeEvents
};