. .

window, Node.js global , .

globalThis . Chromium globalThis , (polyfill) .

window . window globalThis .

.

alert("Hello");
//   .
window.alert("Hello");

let const var .

var gVar = 5;

alert(window.gVar); // 5 (var     window  )

, . .

var let .

let gLet = 5;

alert(window.gLet); // undefined (let       .)

, .

//    (current user)       
window.currentUser = {
  name: "John"
};

//      currentUser   
alert(currentUser.name);  // John

//   'currentUser' 
//       window     
alert(window.currentUser.name); // John

. ' , .

.

Promise . Promise alert .

if (!window.Promise) {
  alert("   !");
}

"" .

if (!window.Promise) {
  window.Promise = ... //      
}

• .

  Array , window.innerHeight( ) .

• globalThis .

  ' window, Node.js global . globalThis , ( ).

• , .

• , var .

• , window.x .