Detect when your site is visible to users

document.onvisibilitychange = function () {
          document.visibilityState === "visible"
             ? (document.title = "👋 Hello")
             : (document.title = "😟 Bye!");
       };

Có thể bạn đã miss một số snippets code

Convert Array-like to True Array

JavaScript: async/await with forEach

JavaScript: async/await with forEach()

Promise + gì

promise + gì

Spread Operator for Objects

Using the spread operator during an Object declaration will assign the properties of the referenced Object to the new Object.

Kiểm tra định dạng email bằng Javascript