fix: use globalThis polyfill instead of self/global

In order to fix the "self is not defined" issues in Android 8 and React
Native.

Backported from master: 3f3a6f9

lib/globalThis.browser.js

@@ -0,0 +1,9 @@
+module.exports = (function () {
+  if (typeof self !== 'undefined') {
+    return self;
+  } else if (typeof window !== 'undefined') {
+    return window;
+  } else {
+    return Function('return this')(); // eslint-disable-line no-new-func
+  }
+})();

lib/globalThis.js

@@ -0,0 +1 @@
+module.exports = global;

lib/transports/polling-jsonp.js

@@ -4,6 +4,7 @@
 
 var Polling = require('./polling');
 var inherit = require('component-inherit');
+var globalThis = require('../globalThis');
 
 /**
  * Module exports.
@@ -30,15 +31,6 @@ var callbacks;
 
 function empty () { }
 
-/**
- * Until https://github.com/tc39/proposal-global is shipped.
- */
-function glob () {
-  return typeof self !== 'undefined' ? self
-      : typeof window !== 'undefined' ? window
-      : typeof global !== 'undefined' ? global : {};
-}
-
 /**
  * JSONP Polling constructor.
  *
@@ -55,8 +47,7 @@ function JSONPPolling (opts) {
   // we do this here (lazily) to avoid unneeded global pollution
   if (!callbacks) {
     // we need to consider multiple engines in the same page
-    var global = glob();
-    callbacks = global.___eio = (global.___eio || []);
+    callbacks = globalThis.___eio = (globalThis.___eio || []);
   }
 
   // callback identifier

lib/transports/polling-xhr.js

@@ -9,6 +9,7 @@ var Polling = require('./polling');
 var Emitter = require('component-emitter');
 var inherit = require('component-inherit');
 var debug = require('debug')('engine.io-client:polling-xhr');
+var globalThis = require('../globalThis');
 
 /**
  * Module exports.
@@ -403,7 +404,7 @@ if (typeof document !== 'undefined') {
   if (typeof attachEvent === 'function') {
     attachEvent('onunload', unloadHandler);
   } else if (typeof addEventListener === 'function') {
-    var terminationEvent = 'onpagehide' in self ? 'pagehide' : 'unload';
+    var terminationEvent = 'onpagehide' in globalThis ? 'pagehide' : 'unload';
     addEventListener(terminationEvent, unloadHandler, false);
   }
 }

lib/xmlhttprequest.js

@@ -1,6 +1,7 @@
 // browser shim for xmlhttprequest module
 
 var hasCORS = require('has-cors');
+var globalThis = require('./globalThis');
 
 module.exports = function (opts) {
   var xdomain = opts.xdomain;
@@ -31,7 +32,7 @@ module.exports = function (opts) {
 
   if (!xdomain) {
     try {
-      return new self[['Active'].concat('Object').join('X')]('Microsoft.XMLHTTP');
+      return new globalThis[['Active'].concat('Object').join('X')]('Microsoft.XMLHTTP');
     } catch (e) { }
   }
 };

package.json

@@ -69,7 +69,8 @@
   },
   "browser": {
     "ws": false,
-    "xmlhttprequest-ssl": "./lib/xmlhttprequest.js"
+    "xmlhttprequest-ssl": "./lib/xmlhttprequest.js",
+    "./lib/globalThis.js": "./lib/globalThis.browser.js"
   },
   "repository": {
     "type": "git",