appear-polyfill/lib/index.js

[](https://www.npmjs.com/package/rax-appear)

"use strict";

exports.__esModule = true;
exports.setupAppear = setupAppear;

var _intersectionObserverManager = require("./intersectionObserverManager");

/**
 * Simulate appear & disappear events.
 */
// hijack Node.prototype.addEventListener
var injectEventListenerHook = function (instances, Node) {
  if (instances === void 0) {
    instances = [];
  }

  var nativeAddEventListener = Node.prototype.addEventListener;

  Node.prototype.addEventListener = function (eventName, eventHandler, useCapture) {
    var lowerCaseEventName = eventName && String(eventName).toLowerCase();
    if (lowerCaseEventName === 'appear' || lowerCaseEventName === 'disappear') (0, _intersectionObserverManager.observerElement)(this);
    nativeAddEventListener.call(this, eventName, eventHandler, useCapture);
  };

  return function () {
    Node.prototype.addEventListener = nativeAddEventListener;
    (0, _intersectionObserverManager.destroyIntersectionObserver)();
  };
};

function setupAppear(win) {
  if (!win) {
    if (typeof window !== 'undefined') {
      win = window;
    } else {
      return;
    }
  }

  (0, _intersectionObserverManager.createIntersectionObserver)();
  return injectEventListenerHook([], win.Node);
}